I would hazard a guess that all it is that she turned three months old
It's at about that point when babies start waking more fully between sleep cycles. Most find it a bit harder to go back to sleep for another sleep cycle, and consequently wake more (even if they're not properly hungry).
Some seem to get used to it quickly and go back to being excellent sleepers. Some, like my two little ones, are dreadful for a few months. I think it's basically luck of the draw.
There are things you can do to help - like making sure there isn't any sleep associations making things hard (say they're used to you rocking the bassinette to get them to sleep... now when they wake up after a short sleep its no longer rocking and they find it hard to settle back down without it). Or put in some sleep associations that might make things easier (if they're used to going to sleep with white noise, and they wake up and its still playing, they might find it easier to settle back to sleep). But mostly I think it's just a matter of going with the flow and knowing it will get better again one day.
Edited by Hopes