My best friend of 19 yrs is married, i am not. She has 3 kids, i do not. We have completely different lives and when i see her i see her with her kids, or with her hubbie around. Thats her life. I don't expect her to come out alone if she doesnt want to. Sometimes she has mad fits of freedom and wants to go out but these are rare.
When someone is contented you are an addition to their life, not a major part like you used to be. Its harsh, i did struggle at the start but you need to accept that this is how it is and try to salvage a changing relationship.
Why not suggest a saturday day time together shopping. Her husband can stay in, fix the car, watch sport or whatever and you girls can go out. You have to fit in with her routine but without being a doormat at her command
Difficult but dont row.... i;ve done that and lost my mate for a year cos she couldnt see my point