It happens.  Even the best of sleepers will have times when they fuss and carry on.  I would say maybe she is teething, and can't really do anything about that.

You say that this started about 10 days ago.  Is there anything that happened around that time that could be causing her stress?  Even something as silly as you changing the sheets with ones she doesn't like could do it.

 I've had this happen a lot with my son.  He's not the best sleeper to begin with, but it seems like right before he gets teeth, or learns a new big thing (like sitting up, walking, words, etc), his sleep cycle gets completely confused.

Ha.  I'm jealous that you EVER had a kid under 5 months that would lay in her crib.  My son flat-out refused to sleep in his until he was about 10 months.  By 12, he was tall enough to climb out.

Don't feel like a failure.  She's probably just adjusting to some change.  My son got his two lower front teeth in that month.  Grin and bear it, and things will probably return to the way they were before too long.

Hi,

Could it be that she is going through a growth spert? and she is hungry. Or she could be teething. I have a 6 month old that did the same thing a few weeks ago but we just continued to do what we usually did and she sorted herself out. Hopefully this happens for you too.