She notices

Fear suddenly grips Megan's face as she feels her shorts beginning to slip. As she grabs down she feels the waistband, discovering it far looser than it was a few minutes ago.

Panic in her eyes she glances up at the unlocked front door and begins to cautiously make her way towards it, hoping to lock it once more.

Not wanting to make it easy on her, you use your powers to snag her shirt sleeve on the counter, suddenly jerking away her makeshift cover. As she spins to grab it, you loosen her shorts further and they slip enough to give you a great view of her bare arse before she quickly grabs them, pulling them back up.

Not content you use a little nudge to draw a passerby into the shop, and as Megan hears the door going she quickly looks around, hoping for somewhere to hide.