I would personally not feed the minute they wake up - especially if they only have a short nap. This would introduce your lo to snacking and would mean that they are not taking a full feed at a time, but rather snack throughout the whole day.
If you don't think that your lo is ready for the 4 hour easy, you could always try the 3.5 hour EASY.
If your lo is only a 3-40 minute napper,it is a sure sign that she is ready to increase her A time. If she is a touchy baby, I would suggest increasing her A time by say 5-10 minutes every few days until your lo is ready to handle a longer A time.
She may just be over tired and this is why her naps are not consistent, and why she is not waking up happy. Have you tried extending naps with Pat/Shhh, PU/PD or Wake 2 Sleep?