I am a long time member but haven't posted for a long time.
I would like some help with clarifying this situation and want to try and establish if I'm just over reacting or if it's something I should be concerned about. It's quite a long story so will try to include as much as I can and not drip feed....
DH and I are have been together for around 10 years, we have our ups and downs but have been through an awful lot together and I think we do usually work through our problems for the better.
An old family friend of DH moved back to the area with her DH and they had a child together. All good, got on really well, kids occasionally play together, had a few social evenings etc.
All good, but I started to notice odd things...DH often works late shifts, on the nights he was coming in late if friend was here having a glass of wine, she would start asking when he was due back and putting her lippy on! He would come home and after endless hints about being tired (for her to leave) I would go to bed and leave them chatting. She's quite overpowering compared to me and would want to organise holidays altogether etc., but we weren't keen as don't get that much time together for hols alone etc. Very pushy in that respect.
She started having problems with her DH, she came over and I asked if she was OK...she said fine, but then overheard her pouring her heart out to DH when she didn't realise I could hear.
It escalated to her being here when I came home from work on loads of occasions...she also knows MIL and would often be there too. She eventually split from her DH, and my DH ended up being there to help...shoulder to cry on, helping with practical stuff etc.
They go to the gym together a few times a week...I've never really fancies it but DH has said if I want to join them I can, so never really minded.
Things came to a head early this year when she had a really bad time with family illness and DH seemed to be spending more time with her. Things were bad between us for a lot of other reasons and we almost separated. We managed to get through things and after talking honestly, DH admitted that although nothing has physical had happened, he could see why this upset me and we realised she had (deliberately?) said / done some things that would cause conflict.
He dwindled contact as at the end of the day, she's still a family friend and it's not my place to dictate who he sees, but I've noticed recently that odd things are happening again...a bit more contact, weird passive aggressive fb posts from her (that might be me being paranoid though)..
Sorry this is so difficult to put I to words and makes me sound like a paranoid horrible person, I'm really not I promise 
Any words of wisdom...what would you do / think?