friendly emails or flirting?

Okay update my Fiance and I have been getting along great no big fights and I am startng to trust..Well this weekend while we are out shopping he spots a girl he worked with and has contact with at work ...So Monday morning he emails her his work as ususal but this time mentions how he saw her at the store and how much she is the face and eyes of her sister and how small she is etc,,he also said he was gonna saw hello but she was there with kids and her sister..well she responds back YOU shouls have said hello...he says next time for sure..Okay he never mentioned he emailed her that to me...He seems to always have a need to connect with some girl at work..Is this flirting? he never sent her anything like this before..I am really concerned that this is the start of him flirting again?