Also know that needles do effect sleep, even days afterwards.
While hunger is a possibility, if she wakes and you can settle her and she stays asleep, then no she probably doesn't need to be fed.
If however the patern she is following continues, maybe try settling at the first waking and then if she wakes a second time feed her and she may in fact stop waking, she is at the age that a growth spurt may have started so try increasing the times for each feed if you can during the day.
No its not uncommon for LO's to loose weight at somepoint, or to stop gaining and just remain the same weight for a while. Especially when they start to move more and are more active in general.