You're about. to be reminded (gently, I hope) of the shipping ban -- pairing Hannelore with anyone is a sore subject; Jeph, most of the characters, and not a few of the forumites are protective of her.
That said, Hannelore as a friend has been good for many of the characters; she seems (to me, anyway) as a catalyst that brings out the best side of many of the other characters, benefiting herself (as in learning how to socialize) in the process. In Marten's case, H. has been the one character with whom he is most consistently learning to give a shit about someone beside himself, with no thought as to what he might get out of it.