Hi!
Have you tried consistently putting her for her naps after 4h A time? Like for 4-5 days in a row? Would she still nap for only 45min? How is waking from her naps, happy and chatty or cranky and crying?
4h A time is a pretty high A time at her age, was she always really high on A times? You can have a look here what is the average at her age:
Average A times- BOOKMARK ME! IIWY I would reduce a bit this A time and would aim for 2 full naps a day, each of 1.5-2h. If one of them is shorter don't worry about it, as long as she is having 2 naps.
I would first do like 3.15h A time for 4 days and if naps for only 45min, wakes up happy and chatty then she is probably UT and you can increase the A time by 10min and stick with it for another 4 days. And so on, till you get better naps.
Is there a reason why BT is so late? Do you want it to be like that and that WU in the morning is around 9-10? Or would you like it all to be earlier?
I think she is waking up every 45min after BT because she is OT from very high A times and not enough day sleep.