Hi
With 45 min naps there could be two issues, a routine one, so your LO is not tired enough to sleep for longer or developmental. Tbh 4 month is a terrible time for short naps.
It is a long time to do pupd for 40 mins to extend a nap, so it could just be that your LO isnt tired enough.
Why dont you try extendig the A time by 10 minutes and do wake to sleep, of they are tired enough patting them through transition is much easier as they are much sleepier at 45 min mark and often will just stir rather than fully wake.
We tried sticking to feeding times, but if it went slightly over i never worried, I wouldnt want to spend 40 minuted resettling just to wake them shortly for a feed.
Wow and she sleeps through the night, thats amazing!