Might be a load of tosh as most of my posts are
but does she get stressed before each dive?
If she does she could experience an increase in her blood pressure which is a common cause of nose bleeds especially if she has delicate veins in her nose.
If that is the case as she gets more experience and relaxes a bit more before each dive hopefully it will stop which could explain why other posters problem stopped!
This is just my 2p and posted as a suggestion not a diagnosis ( I think I have too say that these days
)