This one is easy, rehearse this in your head in your own words, next time you see her just go up with a smirk on your face and say 'let's try that again, hi' and introduce yourself (first name only, it's not a job interview) and ask her name. She made physical contact with you and spoke first, it'd be difficult to see that going wrong. Have a list of inoffensive questions in your head to ask her, does she work locally or some crap like that. What's the worse thing that could happen, besides her turning out to be there to serve papers on you or something....