IMO i would say that it all depends on how much you like her,
theres no harm in trying if you ask me lots of relationships fail for many different reasons but honesty is a must. If when you tell her your preference she runs away then ok it wasnt going to work but who knows, even though she is vanilla she might just turn round and say actually i might wanna give that a go!

lots of people start off like that. Good Luck!