As for 'selling' it to her, in your shoes I'd try to. Both my girls are mad keen on animals, always have been. When younger they always wanted to be 'animal rescuers' (like the TV program), or a more general 'looking after animals'. I've always taken a, 'well, have you thought about being a vet?', line. I've validated their interest, but told them they need to think about what they want in life. Looking after animals at the front line is long hours, low pay. This is fine if you accept making a choice like that will have concequences in how comfortable your life is, your house, your holidays, being able to afford nice things. It's important to do something you like, but if you can do that AND make money, maybe that's the way to go.
At first, to at least some extent, this was probably way over their heads. My older daughter's alway 'got it' enough to express why she might not want to be a vet (she'd not want to put animals down... she was young... ) But it is, I hope, the right approach.
It sucks, but what you do when you are a kid will impact on what you can do when you are an adult. Making that real to her now, i ways that are relevent to her, might help.
To put it into hyperbole, 'do you want to not afford a holiday and live in a nasty house because some kids might be a little mean if you get put into this pragram?' I think of it as the 'do you want fries with that' approach.
My fiance says to ask her if she thinks it is nice for her friends to be mean to her because she has a really cool opportunity, and if they are, are they real friends?
All the best.