She is getting a good long naps in there and she's getting about the 'average' amount of day sleep for a 4mo anyway, so if the three catnaps and one longer nap works well for your family, keep it going.
We can only get short naps at home (40mins) but have just posted in Naps as she is often quiet after waking for up to another 40mins & I'm wondering whether to try leaving her in her cot for that time.
This is your clue that its probably time to increase - she may only need a touch more but just be aware that babies can be stuck in their A time if its not increased then it sometimes all goes to pot in a big way. If its all working, not need to fix it, but if she's having too many short naps, it can eventually catch up with you. A little 5-10min increase may be the way to go since she struggled with 15min - I'd suggest being there at 30min into the nap just to help her through if she is struggling the first day or two of the increase.
That short first A time can contribute to long happy NWs or multiple NWs in the early hours of the morning, so definitely worth increasing that one if those things start happening and they bother you but otherwise, if it ain't broke, don't fix it.