Beth, I am so sorry to read about your fears, I really wish it was one thing we could all not have to face. Some people can’t deal with change, but you owe it to her to talk to her about it and above all, you owe it to yourself. Sweetie, I know you love her, but if you are not fully honest with her then you will end up resenting her, remember what people tell new parents to take care of your new baby you have to take care of yourself. At the same time, you have to be fair to her and let her have all of the information.
It will take time and talking but you have to take the chance, I personally fear the alternative. I apologize if this comes off (this kills me to censor my self but this word gets a lot of knickers in a twist so I will) C-bombish. I do hope that whichever way you go works out but I really think not giving her a chance to love the real you is bad for both of you. If you fully talk it out she may just surprise you and be more understanding and okay after all you fell in love with her for a reason. I am here for you if you ever need to talk to someone or scream at and call names.