Correcting My Step Daughter??

So my fiance has a custody hearing on the 9th finally regarding his daughter. She was removed from the home because her mother and the mom's bf were selling drugs and producing them inside the home. Not sure if there was use going on though. So she's been with us since 12/14. It was rough at first but she has adjusted well and doing very good with us and her siblings. We have recently started writing to her mom and made a few cards for her and sent and gotten responses. Also her mother has call time so she has called just the once so far. The mom's family has requested we take my step daughter to the jail to visit with her mom but she doesn't ask about her mother and recently has started calling her mother by name. So if I show pictures she says oh that's "Sally" not her name but you get the point. We don't feel it'd be good to take her there at this point in time as she is very confused. So should I correct her every time she says Sally instead of mom? Because she calls me mom and it confuses her to death. We tried getting her to call me by name but she chose mommy. I feel guilty if I didn't correct her but at the same time I kinda feel it's fitting like she lost that privilege, that title. Please help