I'm my girlfriend's sisters beta

I've been friends with my girlfriend since I was a little kid. She's smart, kind, and beautiful. I never had a crush on her sister but I definitely stared at her since she looked so much like her, just older and more mature. In high school she had the reputation of being the town bike and she made no effort to disregard the rumor. She liked sex and made no effort to hide it. She looked nearly 1 to 1 with my crush except she had bigger boobs and wore much less conservative clothes.

Years later me and my crush got together and I wound up making fast friends with her older sister. We talked a bit about fashion and past partners and it wound up with her sending me fit checks most mornings.

She never lost that "sexual drive" and she would tell me about her new partners. I suppose it's not 1 for 1 with the definition of beta but I certainly feel like one whenever I talk to her. I don't have much to add at this point so I figure I'll just add my favorite outfits she's sent and my favorite sex stories she's told me.

She sent me an outfit with a normal top and some pretty tiny shorts. It was pretty normal until she sends me a photo from behind asking "is this to much???" Her ass was eating half of those shorts, an amount of ass was hanging out of those shorts that I didn't think was possible outside of movies.

A much simpler outfit was a tight fitting black dress with a LOT of cleavage on display. If she jumped they'd be exposed to the world.

I received a message going "Hey I'm dressing up as a slutty cowgirl but I'm worried it's to much to wear outside, wat you think???" And she sent me possibly the sluttiest outfit I've ever seen counting the costumes I've seen in pornos. It was a short sleeve, pink striped, crop top, tied into a knot all the way under her breasts exposing an insane amount of cleavage, cowboy boots going half way to her knee, a tiny, tiny, tiny pair of shorts that exposed almost all of her pale thighs, and a cowboy hat that complimented the outfit. Being a good friend I should have said "No that's to much to wear people are gonna get mad or worse" instead I wrote "send a picture from behind so I can tell." When I say over half her ass was out I don't mean that a lot of her butt was exposed, I mean over half her ass was clearly on display. I did tell her it was to much and she decided to replace it with a sexy nurse outfit she had from last year.

In terms of sex stories she's told me the highlights would be-

She told me about hooking up with the biggest asshole in school and how he had such a tiny dick. She was dying laughing over the phone about how confident he was in such a tiny dick and that it was barely 4 and a half inches long. As someone into SPH hearing her laugh at someone 1.5 inches longer than me having a "baby carrot dick" was incredibly hot.

This isn't a horny sex story but I was dying laughing listening to it. She was hooking up with a guy she knew for the second time. They were in a hotel room together and the guy starts shaking and he goes instantly flacid. She's confused and looks behind her where the guys staring wide eyed and sees what looks like a hanging guy and she screams causing him to scream, grab her hand, and run into the bathroom. Eventually she reaches her courage to turn the light on and peek out toward the "body" and sees it's just a lamp with a sheet on it. Neither are sure why the sheet was on it but both were convinced they saw a dead body for a good 15 minutes.

Me, my girlfriend, and the sister were all hanging out together and I noticed she was walking a bit funny. I asked if she was ok and she got a smirk on her face and told me she would tell me later. Sure enough after me and my gf get home and she's in the shower I get a call from her and the first thing she asks me is if I've heard the stereotype that asian men have small dicks. She then proceeds to tell me that she got with this asian guy and assumed he'd have a small cock before he pulled down his pants and revealed "genuinely 9 inches." She talks about how he stretched her out and how she "was squirting all over his dick." Hearing her talk about getting fucked by a guy with a much bigger cock than me and using terms you'd hear a pornstar way made it super rewarding to be her beta. I ended up using one of her fit checks to cum in less than a minute the moment the phone call ended.