Ya but despite the fact you've been with her for 6 mo, you are doomed :( been there, done that (with a relationship I'd been in for 5 years many many years ago when I was young), it's a terrible thing for her to say to you, not without some mitigating words at the same time during the same discussion. Time from her - move on!
She (whether she thinks so or not) as harpooned your relationship and it may take you a long time to build up trust like that again (took me 4 years)
females think males are insensitive at times - ha ha
Think of it this way bruh you guys were in a relationship for 6 months if she didn't like your size or wasn't satisfied she would've left along time ago but instead u got her staying for more so clearly your doing something right your the man in her eyes
That's a shame that you and your girlfriend got into the size issue, after the way she responded. You started the conversation, but she could have built you up and made you feel good about yourself and your relationship, but instead she jinxed it. You could remain friends, but keep your clothes on, as I think that intimacy now is a dead issue with her. Of course, if she apologizes and tells you that size does not matter, and so on, then maybe things would work out, but I feel that the damage has been done.