3yrs old interested in kissing

two weeks ago my 3yr old neice grabbed my face and kissed me . After she did this she said"Dont tell anybody". I informed her not to kiss me or anyone on the mouth anymore. She used to give us kisses but by her saying what she said that truely concerned me.  Today her mother called me and told me that she kissed her and tried to put her tongue in her mouth. She asked her where did she get that from and she didnt say anything and appeared to be embarrassed. Is this normal or are we being overly concered?

[Sarah1013]

I dont think you shouldnt let her kiss you anymore. She just needs to know that she should only kiss family and that she doesnt use her tongue. And someone should try to find out more about why she said not to tell. Does she go to preschool? Maybe one of the kids there kissed her like that and told her not to tell.