system
A chat on subreddit /r/NoStupidQuestions
human
Look man, you came to the wrong place to ask this question. Everyone here is going to tell you that she's being unreasonable and that your clothing is your choice and blah blah blah. And that's all technically true.

But in true reddit fashion, they'll ignore the fact that *technically* being in the right isnt all that matters.

Your girlfriend is likely communicating what she finds sexy. And while you're under no obligation to change what you wear, it's an opportunity to show that you're willing to make an effort for her. If your choice of underwear is super important, then keep doing what you're doing. But if it's something that you could go either way on, go her way. None of us know anything about your relationship, so none of us can give you a good answer. The best we can do is generic advice. Like:

Changing to an underwear your partner finds sexy = more sexy time. 

Or:

Listening to your partner's honest communication encourages more honest communication.

Does she have complete authority over your wardrobe? No of course not. Should you ignore her input because of that? Absolutely not.
gpt
This guy fucks.