Marriage is no small thing to consider. Spending the rest of your life with one person.
And everyone looks for different things. It sounds cheesy, but be yourself!
Does she know your intentions?
I'm kind of in a similar situation myself at the moment.
But no, I don't think that she would think badly of you. Depending on how you told her, you may just have scared her off a little. You never know, she may return the feelings and she just doesn't know how to begin to express them. Any girl wold be flattered and a little bit overwhelmed at the sudden prospect of marriage. Even if she does like you back, sometimes things like that can be a little awkward.
If she was your friend to begin with, I don't see why she should be so eager to break off the friendship completely. Even if she doesn't like you!
But, if she's acting stand offish, just give her some time. She may be waiting to see if you were serious, if you really want to marry her. Let her know you still like her, but don't push her to respond. Once she seems comfortable with things again, just ask her out for coffee or something and talk about it. Let her know your not pushing her into anything, you just like her very much.