if you're absolutely set on it, then start now!
Start taking lots of photos, invest in a good camera and just take heaps of photos. Look around for competitions and stuff to enter and send in your photos. You could also go around to small clothes shops in your area and ask if you can take photos...
I think she's just giving her a bit of a nickname, my grandparents always used to call me Erinka and my name's Erin.
If it really bothers you though then just sit her down and tell her. She's a grown woman and if you say it to her nicely i'm sure she'll get the point.