What IS the problem here?
It is that you are uncomfortable and not ready to reveal yourself to your friends/family at this time. This has nothing to do with her, it is all about you and your feelings. Sounds selfish, but it isn't.
When you have sorted them out, they'll be sorted out. You are a teenager, you can't be expected to know everything all the time....though many teens think they do know it all.
If this person cared for you, she would respect your feelings and fears in this matter. The same way you are respecting hers. She wants to not sneak-around...you understand and feel accordingly, but you cannot change the way things are until you are READY to face the results of the announcement.
I think she is pressuring you unnecessarily. She may be comfortable, but you aren't her...you're you. She needs to love you for who you are and not try to make you change to suit her timetable.
I'd be saying the same thing if this were a boy/girl or husband/wife relationship, too. Respect and love don't try to change people to suit their ideals at the cost of the other person. Period.
hh