Ouch! I know exactly how you feel. My first time ever on a mountain bike my husband made me go clipless and on a tight single track trail. I fell so many times, including over the bars. But, if you keep at it you'll learn to love the sport. You should try and easy trail and if there are hills you are unsure of, just get off your bike and walk them.

Also, have you checked if there are any girl rides/groups you can join. I know here they have no drop girl rides and they are nice to start with. Also, they have a womens mountain biking worshop every year for beginner/intermediates where they teach you the skills you need to mountain bike and will help you along tough areas so you don't get hurt. They'll help you with any skills you're having troubles with and break some of your fears on the trail. I've never participated, but I've heard a lot of good things about it and hope to participate next year. You should definitely try looking in to some of those things in your area.