Ok, so general rule of thumb is:
20min naps are typically pain or overstimulation
30min naps are usually OT
40-45min naps are mostly UT or developmental as the sleep cycles become more pronounced.
At this age and depending on how long she takes to feed, she may really only need to be awake for a feed and a nappy change, so maybe even 45min.
Does she sleep longer on you or with white noise? She's still in that time of transition from womb (which is NOISY) to outside world where we often try to keep the house quiet for sleep.
Do you have the TV on? I used to run it for 'company' as I was going out of my mind being at home with a baby but when I turned it off, L slept much better.