Nap training advice

Has anyone ever done nap training? Any advice? My daughter is 6 months old today and suddenly is fighting naps tooth and nail. She’s always been a good sleeper but she’s all of a sudden rejecting her pacifier which used to allow me to easily get her back to sleep if she woke up too early from a nap. She sleeps great at night and is always in her crib and gets put down awake. I let her cry it out yesterday for the first time and hated it, though I’m willing to commit.

I wish I could be more flexible with her day to day but my mother-in-law watches her 3 days a week and she totally panics when the day doesn’t go as expected. It adds so much extra stress and pressure to keep the baby on a rigid schedule.