...it can be hard for MAPs to find love, and if we are lucky enough to have our attraction extend to adult women, and we find one, that's great. If they have a daughter that is in our AoA or who will be in a few years, then yes, things might get dicey when the time comes. Even if we are law-abiding, which the majority of us are, it can cause a rift between us and her mom, especially if our AoA only goes so far and the woman eventually ages to the point that we lose all physical, if not also emotional, attraction to her.
There is also a chance, of course, that if things work out, and you the little girl may bond in a way that never lends itself to a romantic attraction as she ages into your AoA. Only time will tell, so it's a judgment call.
So, my advice is to keep all of this in mind going in, try to bond with her daughter in a way that will be purely emotional as time goes on with no romantic component arising to complicate matters in the future. In the meantime, enjoy your platonic social time with her, and enjoy good romantic time with her mom and do your best to love her as she may come to love you.