Hi there,
It sounds like she no longer has the ability to self soothe or send herself off to sleep, hence why she has regressed back to 45 minute naps and waking in the night. I think using PU/PD will help her to learn how to soothe herself to sleep and for naps, but you will have to get your Mum on board to be consistent otherwise it may take some time to sort out.
Perhaps if you put a weekend aside to work on naps/bedtime using PU/PD then by the time she goes to your Mum during the week, Mum will only have to do a few PU/PDs to get her to sleep...hopefully!
I think at 10 month we just used the PD part of PU/PD with Mads - when she got upset we would use our voice to reassure her and a hand on her tummy/back and then wait until she stood up before gently laying her back down again and reiterating that its just bedtime honey, time for sleep. When she calmed, we tended to step back from the cot to try and get out of her vision but if she got upset, we would repeat the process again.
Good luck!
Dee
x