Nap time frustration

I am feeling very frustrated with putting one of the babies I care for down for naps. I’m doing a nanny share with two almost 15 month olds. I started when they were 8 months and both needed to be rocked to sleep, but shortly after one dropped to one nap and is able to fall asleep on her own in her crib. The other is still on two naps (even though I think she is ready for one) and needs to be rocked to sleep for almost 30 minutes. And in order to keep her second nap which is about 45 minutes I have to wake her up after an hour for her first. At this age it feels insane to rock her to sleep for that long. Everytime I’ve suggested we try one nap her mom says she’s not ready for it yet and she doesn’t want to push her into it. She also doesn’t really let her cry when I’m not there for other things either like not being picked up immediately or having to sit in her high chair to eat. So trying to transition to not rocking her will be difficult and I’m scared to bring it up to her mom since she usually shuts me down. MB is actually very nice too and isn’t rude when she does this she just seems generally overly anxious. Like when I first started she requested I only let the babies play with their own toys to not spread germs, which I agreed to but quickly showed her this was unreasonable as they aged also it’s better for their immune system in the long run to let them spread the germs a bit. Anyways just a point about being anxious. But it’s hard to ease her and give suggestions when she doesn’t listen I’m thinking of just changing her schedule to one nap the next two days and not ask her and see how it goes. Since when I’ve made decisions like this in the past she seemed thankful after. And I think she won’t need to be rocked so much if she’s actually tired when we put her to sleep.

Has anyone had an experience like this? It’s becoming so frustrating to get her to sleep and she gets so upset like cries for 10-15 minutes when she realizes it’s nap time. To be fair she will regularly cry for 2 minutes for a nap if she’s actually tired but then will just sleep.