Hi Melissa,
At this age, most babies have an awake time between naps between 1-2 hours so I would also take that into consideration for your baby when looking at her overall schedule and day time sleep amount.
And yes, typically, we do believe that good daytime sleep helps with better nighttime sleep. Your doctor's recommendation seems to be based on thinking that your daughter is waking at night because of too much daytime sleep. And that could be true. However, there could also be other reasons for her waking and I would be worried that if too much sleep during the day is NOT the reason, then by going in and waking her early from naps, may actually create more problems.
Now, without many details about how she wakes at night, now she falls sleep or how she goes back to sleep, I can't really speculate what else might be contributing to her night wakings. However, for a baby this age, it is not uncommon for them to still need 1-3 feedings at night. And this could certainly be true for her if she's sleeps 4-5 hours during the day and she may not be getting enough to eat during the day.
You might try seeing if you can get more milk to her during the day to see if that helps. Also, make sure she is only feeding until drowsy either at bedtime or when she wakes and that you are laying her down still awake so she learns to fall asleep on her own (if she hasn't already) because this might also be a factor in her night wakings.
Here is a post on 4 month schedules that you might also find helpful:
http://www.babysleepsite.com/s…..-schedule/
Keep us posted!