Sorry you have to go through this
If you feel you can send her back i would be certain of what the breeder will do with her. I say this because some breeders will just put them to sleep
Lp is managble and if it gets to bad there is a surgery to fix it and then there will be no more problems
. I wish you well it's not an easy desion
What grade is the LP? If it is 1-2 it is very minor and she will probably live a heathly normal life with no problems if it's a 3-4 them she might need surgery. Maybe ask the breeder for a partial refund because she will need surgery (if she needs it)