The seemed might friendly. Should I be concerned?

My husband and I have been together some 20 years, married for 11. We both have had some infidelity issues in our relationship since we started dating. Yes, we are in counseling to deal with some issues, that being one of them. My husband feels that what he did 7 or 8 years ago should have been long solved by now but every time I see him speaking to someone else those thoughts and feelings come back up for me.

At our church he is a very outgoing person. He's a deacon so the pastor has him on several auxiliaries and committees where he has to talk to multiple people constantly. Yesterday he was asked to lead Sunday school for the entire congregation on our weekly zoom call and after it was over a number of people congratulated him on how good of a job he did. Our church services are streamed live from the sanctuary and one Sunday a month he does the welcome on camera. We had our newest granddaughter christened yesterday along with a number of other babies and kids in our church so there were a few more people there than normal. After service people were still talking to him about how well of a job he did during Sunday school so as we were walking to the car to leave I was putting one of our grandkids in the car and he was a few steps behind me. When he got to the car there was another attractive girl walking by and he struck up a conversation with her. He said something to the affect of it was good to see her again and I heard them talking about how she normally just watches the live stream at home but today she decided to come into the building. When I noticed they were talking I casually spoke to the girl and she spoke back to me but she sort of gave me a cold response (according to me). When I got home I asked my husband have they spoken before. He said no but since she normally doesn't come to the sanctuary he hadn't seen her since Dec he was just being nice and speaking. This girl is a very tall and attractive young woman. My husband seems to always be in somebody's face talking to them. In the past few months my husband has friended a number of the church members on Facebook (no, not all female) including this girl and I just wanted to know if they had ever spoken before. He feels I'm just looking for something / anything to rehash what he did 8 years ago. Should I be concerned that he seemed to be very friendly with this girl?