Not exactly, she gets seen

Based on ideas originally by Consensueros.

Mackenzie was panicking. She was standing there, in just her underwear, with her arms essentially stuck above her head. If she lowered them, the engine would be lowered too, right onto Alex's head. But she couldn't have Alex move out of the engine's way without him pulling his head out of the car. And he did that, then he'd see her exposed state for sure! She needed to figure out a way to get Alex to keep working on the car, but to be able to cover herself up as soon as he was done.

Alex, meanwhile, had just encountered a predicament of his own. When he'd first began working on the car, bending over deep into the hood, he'd noticed an old side-view mirror resting on the floor below him. It was apparently discarded, and Mackenzie likely didn't even remember it had been there. But it had just so happened to be angled perfectly for Alex to see Mackenzie standing there while she'd kept the engine aloft. He'd been content to occasionally glance at his cute friend while he was working, and figured it wasn't even worth pointing out to her that she'd left an old mirror on the floor.

But that had all drastically changed when Alex had glanced at the mirror again, only to see Mackenzie standing there in just lingerie! He'd tried to keep his composure, only sputtering slightly in shock, before trying to figure out what he should do. His gorgeous friend (who he'd always had somewhat of a crush on, if he was being honest) was there on full display! Face red and pulse pounding, Alex prepared to stand up and let Mackenzie put the engine back down.

"M-Mackenzie..." he said as he began rising, already preparing to avert his gaze.

"Don't stand up!" she hurriedly cried, not knowing she'd already been completely seen. She was torn between wanting to get her arms free as soon as possible and wanting to remain unseen by Alex for as long as possible. "I mean, uh, let's hurry things along, yeah? I don't want to see your head out of that car until you're done working on it. Let's go, chop chop!"

"...Alright," Alex said, returning to the depths of the car. This gave him the astoundingly rare opportunity to check Mackenzie out as his leisure, and at her own insistence nonetheless! There she stood, face already a deep shade of red, eyes flitting all around her. Whatever had happened to leave her like this, clearly the redhead hadn't intended it. His eyes travelled over Mackenzie's large breasts, only half concealed by the sexy strapless pink bra she was wearing. Then down her toned stomach to the matching pink panties, complete with a little bow on the front. Before today, the most undressed Alex had ever seen his friend had been in a bikini. And, he supposed, although she was technically showing a similar amount of skin at the moment, this felt far more intimate than a day at the beach. The broad shouldered man gave a silent thanks that his waist was pressed up against the grille of the car, completely hiding the growing bulge in his pants.

"So, uh, think you'll be done soon?" Mackenzie asked awkwardly. Only then did Alex realize he'd completely stopped talking after seeing Mackenzie's exposed state.

"Oh! Uh, well..." he said, mind racing. He felt bad that Mackenzie had somehow wound up in such an embarrassing situation, and genuinely wanted to help her. But then again... he'd already seen everything, so what was the harm in stretching things out a little longer? Besides, as soon as he was done he would help Mackenzie out of her predicament.

"I don't know, Mackenzie," Alex said. "This might take me a while yet."

"...How long is a while?" she said softly.

"Hm, 20 minutes? Half hour? Why, you got somewhere to be?" He watched her face grow more nervous with the estimates. He wouldn't let her actually suffer that long of course.

"W-well, I do have other s-stuff I wanted to work on this afternoon," Mackenzie stammered.

"Oh? Like what?" Alex began, very slowly, raising his torso from the car.

"Hey! Head down!" Mackenzie blurted out in a panic. "A-at least until you finish up!"

"Whatever you say," Alex said with a chuckle. He had to admit if was fun teasing his friend.

Mackenzie, meanwhile, had come up with no plausible way out of her dilemma. Her only idea was to crouch down and yank her jumpsuit back up the second her hands were free, praying that Alex didn't immediately look her way. She wondered if she could think of a way to innocently get him to look away from her as he rose from the car. But her thoughts were interrupted by a very soft popping sound and a strange sensation around her chest. The mechanic wondered for a moment what it could have been, before hearing a soft tink! She glanced down at the floor, noticing a tiny curved piece of metal between her feet. For a moment, the redhead was perplexed, but then it dawned on her.

One of the hooks of her bra had just snapped completely free! Somewhere between the damage the bra had taken earlier and its current lack of shoulder straps, the old undergarment was breaking apart. Apparently, it could no longer do its job of supporting Mackenzie's impressive bust.

"Oh please no..." she whispered to herself, suddenly realizing that what she'd thought was a worst case scenario could, in fact, get a whole lot worse.

"Hmm? You say something?" Alex asked.

"Uh... I, uh, said..." Mackenzie stammered. She needed to get her arms free pronto! "Do you think you could call it here for today maybe? Just come back and finish up tomorrow?"

"No can do my friend," Alex said, still watching her squirm, but having no idea that her bra's clasp was failing. "If I hurry, I think I can finish in about 10 minutes, sound good?"

Mackenzie felt another pop and her entire bra shifted a fraction of an inch down her chest. Another hook had failed and fallen to the floor with a soft sound. That only left one remaining hook doing its job. One tiny metal hook was the only thing shielding the beauty from utter toplessness. And it felt like a single twitch of her body would seal the deal. Mackenzie didn't respond to Alex's question. She didn't dare speak. She didn't even breathe. She stayed as still as possible, silently pleading for the last hook to somehow remain intact.

But it wasn't meant to be. Before even a full minute had passed, Mackenzie simultaneously heard and felt her bra clasp fail completely. In what felt like slow-motion, the beautiful woman looked on in horror as her bra tumbled downwards, completely baring her breasts to the open room and to the surreptitiously watching Alex.