What is she doing between 2-6 when the mistakes are happening? Is she loose in the house playing with someone? Laying quietly sleeping? Until a pup fully grasps the whole idea of where doing there business is acceptable and where it is not, with some pups you have to work harder / more often in getting them out the door. If she is playing during that time, as soon as that play stops take her outside. If she's laying quietly sleeping, as soon as she wakes up take her outside.
Is sounds as if she understands that the kennel is out of bounds but the house is not. Depending upon who's in charge during the afternoon, she may be giving small signs like a walk past the door to go out or even just walking toward the door ... No whimpering or whining. Also, are you using the same door to take her out all the time, so that there is no confusion as to where in the house she should be alerting someone to take her out? If you are allowing her some freedom in the house, you (or who ever is in charge) will need to watch her like a hawk so that this does not become the norm vs a mistake.
As was also mentioned, there is the potential of a bladder infection, but if she is making it through the night I would think that this is not the case.
We just went through this recently with a pup, tested for a UTI, not the issue. He just seemed to be a slower learner for housebreaking and we ended up watching him like a hawk and wearing a path in the floor in getting him out the door as soon as he made a move towards the door. Even went so far as to pick him up to get him out the door ASAP and not give him the opportunity to stop part way there. Took a little longer than the norm, but we got there and you will too!
GMHR-III Dakota Creek's Royal Navigator MH (AKC & CKC) (NAHRA 500 pt club)
MHR Pine Acre's Dakota Sand Creek SH WCI
MHR Dakota Creek's Royal Gem
WR Dakota Creek's Wreaking Havoc SH