Alright, here we go:

Consent is crucial. I wouldn't advise you just stay quiet/cut off communication with her, but I also wouldn't advise over-doing the contact. Give her space to reflect, to think, and to gather thoughts, to heal from feelings she's going through. Especially with anxiety, (me included) we tend to state things right away with no contemplation, but rather based on the impulse feeling at that very moment. And do both of yourselves a favor and be completely honest when you reach out to her. Say you were genuinely under the impression she was completely okay with this (if that's the case, of course). You're not vulnerable for apologizing, you're vulnerable the moment a woman feels violated, however women are vulnerable to feeling violated in all kinds of ways, all the time. It's a vulnerable situation altogether. So please don't feel like apologizing won't help. And, the term "rape" is sadly a loose term these days. This does not mean we shouldn't take it seriously--it is incredibly serious, and traumatizing. But we should also understand a situation before we say it was rape. Bottom line, after a genuine apology, leave her alone to think, and to make sure she doesn't feel pressured. From your post it seems like you truly believed there was no foul play, that see consented, that it was okay. She wasn't vocal, and perhaps her inner worries stayed inside and on the outside she seemed like she was okay with it. You must tell her if you would have known she was not comfortable, you would not have proceeded. Again, only if that's true. I'm not telling you to feed her lies. I wish you good luck. This will probably be okay, and end up being a hugely important learning experience!