I know somebody that their kids did this. (they were eating sandwiches on my porch and mayo dripped out from the sandwich and they both fought over who was gonna lick it off the concrete.) You could ignore the behavior but I don't know that that would do any good. So the other thing you might do is take away her favorite things movies, stuffed animals. No matter what age kids are they have currency such as movies, play dates, toys things like this.
The other thing you could try is timeout. When my kids are doing something wrong I always think what punishment would fit the crime but how do you punish a child for licking things.
Another lady ( it was on a post for talking back her name is Cori b maybe you could send her a message and see what she says. Its on the talking back issue, Jennifer m is who posted it on 3/17) on here said she gives he child(ren) mouth timeouts meaning they can't speak for a certain amount of time. Maybe you could do the same when she does lick something she has to sit and not speak for 4 minutes. I'm kind of at a loss for you but hopefully I gave you some ideas. W.