What sort of routine are you following now - 3 hour or 3.5 hour?
If you think your lo can handle the 4 hour routine and not become overtired, then it would be worthwhile trying, however most babies of this age are usually on a 3.5 hour routine.
If she cannot make a 4 hour feed wise, then stick to a 3.5 hour for now, and she will let you know when she is ready to start extending her times.
Following the 3.5 hour Easy you could still feed at 5;30 and then again at say 7:30 - this is then considered as a clusterfeed to help your lo tank up.
Hope this helps