Most babies drop the catnap around 6 months, so she might be approaching that point. At 5 months most lo's can stay awake for 2.5hrs, so maybe try W7, N 9.30-11.30, N 2-4, and 6.30/7 bedtime.
The 15 mins extra a time in the morning should get you a longer nap. So you can push the day as backwards as possible.
xxx
charm