So this may turn into a bit of a long story.
As background, I don’t have a huge family. Five cousins, three on my fathers side, two (live abroad) on my mothers. Growing up, myself and my brother were much closer to my three cousins on my fathers side- they lived in the same town and the families were close. I have one cousin very close in age to me, and we were very good friends up until we were about 19/20 when she just stopped communicating as much, wouldn’t invite me out etc. Wasn’t a complete surprise, she has done this with lots of friends in the past. Our relationship then became more like cousins- seeing each other at family events only. At the time I had taken this quite bitterly, I had seen her as one of my best friends and I was cut off quite suddenly with no explanation.
Several years ago I got married. My cousin close in age is unmarried, my aunt has a strong dislike to her long term partner. My aunt can be quite a nasty person, and I have long suspected there was a subtle rivalry between my cousin and I, fuelled by my aunt. I think my position of getting married first made my aunt very jealous that it was not her own daughter. Nevertheless, they involved themselves in the hen do and wedding and all seemed fine.
2 years later my marriage broke down very suddenly (my exh basically up and left me one day). My aunt became very involved, visiting my parents much more frequently when I had to move back in. She would start many conversations and ask lots of questions, she even offered me a room in her house should I wish time away from my parents. I took it all at the time as kindness, however looking back now I think she wanted to be involved and to have the “gossip” to make herself feel better about her previous jealousy.
I since got involved in a new relationship. This was possibly quite quick, a couple months, since the breakdown of my marriage. My aunt then felt it necessary to question my parents on the whole situation of my marriage breakdown and wrongly assumed that it had ended due to infidelity on my part with my new partner. I was incredibly offended by this, especially due to the circumstances in which my marriage had ended. Nevertheless, my parents answered her with the truth and I never brought this up with her.
My aunt then began to distance herself, along with the rest of her family to mine. At some point, we were all deleted on facebook. Over Christmas she did not send any cards or well wishes, although she did complain to mutual friends that none of us had checked on her as she was ill. We had not been aware as there was no contact with her 
Last year, I became engaged again. We opted to have a very low key wedding, with very few people there during the day (only very close friends and family) but then have a big party that night. Due to my family circumstances, I didn’t want my aunt and her family there to see me getting married again. By this point I haven’t spoken to any of them in well over a year. We are not close. However, I knew it would cause ww3 if they did not get invited at all, so I sent them all (with cousins partners included) an invitation to the evening event. I heard nothing back from the rsvp, but my father met my aunt in a shop and questioned whether she would be attending, she brushed it off and said they had something else on. Ok fair enough. My father then found out through mutual friends that my aunt had been in tears and complaining to them that she “had not been invited to the wedding”. I can only assume she was offended at not receiving a full day invite, so opted to not attend any part of the event out of spite.
This all happened last year, and there’s been no contact since. I’m now pregnant with my first child and had hoped that perhaps my aunt would have wanted to get a little bit more involved with the family for that reason. We don’t have a big family as I have said, and I really feel bad for my dad that his only sister has distanced herself for what we believe to be very childish reasons. But I also feel quite guilty that perhaps I’ve been the catalyst in all of this and possibly I should suck it up and reach out to her, if only to help mend and develop some sort of family relationship again. Or do I just feel happy in the knowledge that she has decided to do this herself and leave her to it?