Hubby being overly friendly?

First of all, my SO and I have been together for 5 years and in the beginning our relationship was rough. Not a lot of trust and a lot of arguing/fighting. We have been to counseling for years and for the past 3 years our relationship has been a lot better. We now have a 2 year old son and I’m 35 weeks pregnant with our second. I’m a SAHM currently.

Anyway we live in a duplex now and this past summer a young, cute, single mom moved in next door and over the past months her and my SO have become friends..texting each other during the week. First it was about house things but now it seems they are sharing memes and jokes and stuff like that. He lets me see their convos and it’s nothing inappropriate although it is starting to make me feel a little uncomfortable and this is why..she doesn’t really talk to me at all. Maybe once or twice in person, but when she meeds something she texts my SO. Sometimes I’ll hear them outside the apartment chatting and when I come out it’s just awkward and she says like oh I’ll leave you two be and goes back inside. At first, it didn’t bother me because I’m pretty introverted and my SO is extroverted and it seems she is too. But now idk if it’s just pregnancy hormones or what but they were texting last night and I just blew up. I looked at their convos and it was a pretty long convo..more than he ever texts me and he says that’s because he talks to me at home. Anyway, like I said, it’s nothing inappropriate but just like they’re really getting to know each other. Would you be uncomfortable with this or am I over reacting?