It's confusing when things change all the time isn't it.

It is very normal for the duration of feeds to shorten as the baby gets more efficient at sucking. It is quite possible that she is drinking enough in 5 minutes per side. 5 feeds in 24 hours is on the low side for that age but again, it is possible that it's enough. If she is having at least 5 heavily wet disposable nappies (or 6 - 8 clear wet cloth nappies) in 24 hours, is doing soft poos and is gaining weight over a 3 - 4 week period (remembering that this is about the age when weight gains slow down), then she is getting enough.