So, so sorry to hear about your daughter and that she has to deal with this again.

My brother was only recently diagnosed and is just beginning treatment, but he did have some pretty foul smelling breath at the outset and then a tooth just dropped right out of his jaw! The tooth obviously was rotted and because of his tumor, neither he nor a dentist was able to get up there to do anything about it.

You don't mention in your post but does your daughter still have her teeth? Could this be contributing? Just a thought.

My prayers are with you.