Not in itself,no.

If you 2 aren't in a secure relationship and she is wandering,or not really attached to you,perhaps a red flag is warranted.

Let's face real world rules here,we will,at one point in time or another,see people from our pasts, relationships notwithstanding.How a person handles that encounter is what I think makes the person.

Did she lie and say she just happened to see him,or was it in passing that he approached her,struck up conversation?You know,she could have said nothing at all if she was trying to keep a secret.. I say be secure that she at least opened up about it,meaning she has nothing to hide.

JMHO

KBC

... No, just co-incidence...

OK, here's the thing. When we get into serious relationships we feel possessive of the ones we love. It's normal and is actually destructive to a relationship. You need to fight this desire to get alarmed or insecure about your significant other running into someone from her past. Being jealous can be a huge turn-off to most women, better to act like it doesn't bother you because you know "you're the man" even if you feel a bit insecure inside. Just my humble opinion.