I hope one of the ideas below makes you want to play. Feel free to make changes. And I'm always interested in other ideas along the same lines.
Older Sister/Younger Brother
A 24yo woman moves back to her hometown in California after finishing college on the east coast. After finding most of her friends have moved or unavailable she gets her 16yo brother and a few of his friends to help her pick up some second hand furniture and necessities she needs for the new apartment she just rented. The next day her brother returns to help her unpack, move things around and to do some painting. Her eyes had almost popped out when he read the shirt he had worn. It was a white tee that said in bright read letters, 'I Like Girls Who Like Girls'. If he had only known who she had spent most of the last 5 or 6 years with different girls in her bed. When she had left home girls had still been on his yuck list. Now he was a little perv. A brother and sister get reacquainted. I would like to play the sister, but will do the brother if you'd like.
The Goth Dyke and The Cheerleader
The cheerleader has the football captain for a boyfriend. Most of the guys think she is the hottest girl in the whole school. Her parents think she's a princess. She has given oral a few times, but has otherwise kept her virginity. Her study habits could be better but doing a little flirting time with the teachers keeps her grades in the top quarter of the class. But recently things have started to change. The relationship with her boyfriend was on the ropes. He wanted more than just oral and there was a rumor she had heard that he had banged one of the other cheerleader a couple times. That was after he had blown up when he found out that she had given one of the geeks head in exchange for money she needed for pot. Our cheerleader had become a bit of a pothead. Then there was the problem with her clothes. Outside of having become more slutty most of them were shoplifted. Our goth dyke had all the juicy gossip from a cousin who ran in the cheerleader's circle. The goth girl was bitch, chubby, and had a thing for pretty cheerleaders who seemed to be vulnerable. I would like to play the cheerleader, but I will play the goth if necessary.
Ms. Kenner worked in a business office where she had again been passed over for a promotion. She had even gone to bed with the boss a few times in hopes of improving her chances. She knew she was qualified, but she always lost out to a man. She was also becoming known as the office slut. After awhile she began to notice that her boss seemed to take an interest in her 16yo son. Every time he was around the man found time to talk to the boy or show him pictures from his latest deep sea fishing vacation. Ms. Kenner found the man's eyes seemed to drawn to her son's curvy rear-end. Thinking it had possibilities she encouraged her son to accept the offer the man had made to take him camping the following weekend. She knew the boy was girl crazy and had a girlfriend. But if her son's ass could get her a promotion she was all for it. She wasn't sure the man could get into the boy's pants, but if he was successful the next promotion should be hers. Ms. Kenner dropped hints over the next few days that whatever happened on the camping trip she would be sure was kept hush-hush. She hoped her boss understood that she was giving her permission to try and lay her son. I'd like to play the son here, but I can play the boss if need be. The mom could also come into play.