Gawd.
I've had this by the way - okay, I am married, and have been for about 100 15 years.
But I have been told, in no uncertain terms, in the past, by MIL (when I was also married) that I'm not a "real" Auntie, because I'm not a blood relative.
Fast forward to now, and one niece is now at University in my home town (up to 7 hours drive from her home, so quite way from home), and I have done her washing regularly over the past 3 years (not strictly necessary, but hey, and happy to help), had her over for roast dinners, free legal advice, emotional support, taken her to the STD clinic, suspected her health anxiety issue (see STD clnic!) and supported her in getting help from her GP, lent her money, (which I got back), driven her long distances, given her relationship advice when asked for, and so on so forth. Careers advice, referrals, and an internship off the back of it. And more.
Not a real Auntie my arsehole. If I told her her grandmother said that she'd be fucking fuming.
But I won't stir up the shit, because I'm a real daughter in law (or some might say I'm not?!
)
Basically what I'm saying is, going forward, your relationship with this child is dictated by you and the child, and nobody else, not even the parents or grandparents, with consent of the child.