Not an expert by any means, but both my DC have played clarinet at some point, DS still does.
Reed - should be taken out after playing each time, and put back in the little case it was in when it was bought. That way it will dry out between uses.
Replace when obviously worn (ragged edge) or chipped. DS plays his clarinet every day, often several times a day, but still only needs a new reed every couple of months.
Otherwise, use the cleaning cloth that should be with the instrument (if not, buy one e.g. www.musicroom.com/se/id_no/078040/details.html) to pull through after every use to dry out the inside.
Squeaking may be because the rood is not properly aligned on the mouthpiece - loosen the bands holding it on, align the top edges carefully, retighten. It may also be because she's not quite got the right 'hardness' of reed (teacher should advise you on that one) , or because the shape of her mouth isn't quite right yet. Does she get squeaking if playing the mouthpiece only (take it off the rest of the clarinet)? If so, it's a reed / mouth issue. If she gets squeaking only when playing particular notes, not with the mouthpiece only, a key could be badly aligned or she could not be pressing down fully - the latter is technique, the former needs whoever you got the instrument from to adjust it.
The best approach is to send a note in to the teacher (is this individual lessons? Or the dreaded 'whole class' version?) to ask for suggestions of things that you can try easily at home to solve the squeaking. It should also mean that they go over things to look for with your DD in her lesson.