Sex with Megan was awesome. Lying next to hear in bed, you tell her that you loved that so much that you want to do it again, and whenever you want. From now on, she's to be in your room, or wherever you call her to, available, ready and willing to have sex with you whenever you want. If she's in class, that's too bad. If she has family visiting, that's too bad. From now on, Megan's job is to serve you sexually. You reach over and give her tight ass a squeeze. "And no going soft on me, either," you say. "I want to make sure you go to the gym every day." You pause. "For at least an hour ... wait, two hours." Then you smile: do you control her or not? "No, from now on you need to spend four hours a day in the gym. I want you as hot as you can be. And when you're not in the gym, you should always be wearing your makeup. Is that clear?"
"Yes, master," replies Megan, with a sigh. "Hey, stop that," you say. "I want you to look like you enjoy it." She then smiles, and you do too. This is too good.
Sure enough, your plan works like a charm. You have the hottest sex of your life whenever you want, trying crazy shit you'd never bring up with anyone else. You even play around with the gun some more too, shrinking yourself to walk up and down her body or shrinking her to massage your giant cock. Sure, people notice she's starting to spend a lot of time with you, but you just tell your friends (and she tells her friends) that you've just gotten close recently. You don't have to tell them anything.
Unfortunately, you notice one day as you're going through Megan's mail that she's about to fail out of school. She has been missing a lot of class due to your frequent demands for her to please you, and the amount of time she's spending working out isn't giving her a lot of time to study. You realize that this path is going to lead a lot of headaches when she gets kicked out of her school and her family comes around to figure out what the hell's going on.
You figure you've basically got two options. First, you could work the gun some way so that everyone forgets Megan ever existed as her own person. That way people will stop bothering you about what you're doing with her, and the problems of real life like grades and family obligations won't interfere with Megan staying your little sex toy. Alternatively, you could just make Megan your actual girlfriend. That means you'd have to let her go to class and study, but there'd still be plenty of time for sex and games, and you'd have less of a problem going out with your friends and her friends. Megan certainly isn't in a position to complain, and if both of you tell the outside world that you're in a relationship, there's no reason you can't have a public relationship with the hottest girl on campus. Then when you graduate, the two of you could get married, and thanks to the gun, even marriage wouldn't be a constraint on you. Of course, if you made Megan a secret only you know, then you wouldn't have any obligations at all.
Both are tempting choices. Of course, if Megan's failing out of school, maybe that's Megan's problem. Do you really need to worry about this yet?