mimiEliza
I have ever been called by any name in the 14 years I've known my daughter in law, simply nothing. Maybe, referred to Nanny......this or that.... but infrequently. The worst feeling for me though is that the rest of the family are personally named but never me. Very hurtful to be a non entity and highly disrespectful!
Yet maybe she would not like to call you Mum, and thinks it might be rude or might feel awkward about calling you by your first name and would feel it would be too stiff to address you as Mrs Surname as she is your daughter-in-law.
So not necessarily disrespectful, maybe just trying to be polite according to her upbringing and her look on life.
So perhaps say, if you wish to do so "You can call me Auntie Name if you like" and maybe that would work for both of you, family but not too familiar if that is her way of thinking, which it might be.
Alas, I have never been married, but I think that I would have felt Auntie Name would have been best all round if she were happy with that, bearing in mind that some of the people I knew as Auntie were not genetic relations, only related by being married to a genetic relation.
I hope it all works out for you. If so, this thread will have done some good.