Depends on your level. I may have forgotten about exp share and lucky egg. I also didn't use the breeders. I was careful with my EXP, but split six ways and without boosts, you can only get so far.
You missed a battle against her at the start, you can't go back and get it. Run the game in debug mode and increase her affection by I think it's three points. It will be a multiple of five. That will move her. It's been an issue the dev has refused to fix, and something I ranted about above.
There are instructions on how to access debug mode, use the search feature at the top of the thread.