I am an only child so growing up so my cousin was the closest thing I had to a sister and up until i was 6 the same could be said for her. Sadly now I am once again the closest thing she still has to a sister. Us growing up close is not the problem I just thought it would be needed to keep in mind for context so that i make it clear this is a very very very close relationship we had. We even shared a room growing up for a long time.
when she got married 10 years ago I was thrilled for her. I flew all the away to asia for a full month as I was a bridesmaid. I followed all of her wishes to the point. I did not complain about my hair, my nail colour selected by her, the dress she wanted me to wear. I said yes to it all as I understood this is her day and I am here to support her.
Before the wedding I bought her a nice Tiffany's necklace as my gift as i loved her dearly and was happy to get her what I hope is a once in a life time gift. My DM was with me and I asked her if she remembered me buying this just to check I had not somehow got confused with things... it was 10 years ago after all.
3 years ago my boyfriend proposed and I of course said yes. I pretty much told my cousin right after telling my dm just because of how important she is to me. I asked her to be my bridesmaid. Now I will understand if I was wrong here but I did not make her my maid of honour. This was not because me not loving her but because she was all the way in the US. She won't be here for any of the usual bridesmaids duties plus she had a family so this really was more of a symbolic role when it comes to her.
I created a group chat for me and all three of my bridesmaids ( my cousin and both of my future sister-in-laws). I showed them some dresses that I liked as bridesmaids dresses and said I was of course going to pay for them and I wanted these to be one of the gifts I give to them. i took their in put in what colour and what style they would prefer (no pink or light colours) I tried to incorporate as many wishes as I could. Both the other bridesmaids loved the dress I chose in the end as did most people I showed. My cousin said in the group chat she is worried about not fitting into the dress. I kept telling her not to worry and once we get the measurements I will make sure it fits. Again she says in the group chat she is worried about not fitting can she please wear her own dress (by this point I was wondering if she was pregnant with a third child) I again explained saying I will make sure it fits. Fiancé privately told me that his sister did mention to their dad and she found my cousin was being rather rude to me by that point.
One year on she messaged me saying with her daughter being flower girl and her son being pageboy she would prefer it might be easier if she was not a bridesmaid as the kids are so young. I said of course and I fully understood that she wants to be able to make sure the kids are comfortable. I asked her if she would like me to hire a babysitter so she and husband can enjoy the evening do without worrying about the kids etc. She was coy about giving me an answer with a lot of she will let me know closer to the time (hindsight this should have been a first clue what is to come)
So around January she calls for a long chat saying her husband is just starting a new job and might not be able to come it is just her and the kids (they knew the date for 18 months by this point). I said I was very sorry and if the trip would be too hard on her own with the kids I would of course fully understand (a lot of tears saying how she wished it could be different and a lot of me being supportive and saying I understand and I know she cares for me)
This week we talked again and I was saying how much I was looking forward to next year after I had to cancel the wedding this June. She looked kind awkward on the video call and dropped the bomb that due to this pandemic she and the kids would not come either. I assumed it was just her being worried about risks and said right away to not be silly I fully understand she needs to do what is best for her and her family. She then said she was planning to take a kids back home (in her eyes) Asia in the summer (date of my wedding) with her husband as life is just a bit more normal there and my wedding would just not be the same without the ability to travel Europe like she wanted for her and the family. I was a bit taken aback by this point but said I understand her putting her kids needs first. We talked a bit more and talked about family and she said she felt so sorry for my dm who is caring for me gran right now and how we both (my mum and me) just need to be a little bit more selfish. I just nodded and agreed. I asked what her kids would like for christmas so I could still get it to them on time. In the end I picked a mario lego set and a electric pet unicorn for them to enjoy as well as a switch game for her and her husband to play and maybe play with the kids.
This is the same cousin where I dropped everything here in the UK to look after her in the US after her sister passed away and I stayed with her for a full month till one of my other cousins would take over and stay a week or two... (yeah i was the only one to drop everything for a month out of friends and family) I just spend my days keeping her company and being the support she needed. When my mum asked if she took me to see any places I told her no and that I was here to look after my cousin not to go on holiday etc.
She mesaged me asking if I liked pandora. I mentioned I once had one and still have the charms but the chain broke but it's not really a issue as I wear my fitbit these days. At this point she generously messages saying she would love to give me a new pandora bracelet as a wedding gift. Now i did remember giving her a Tiffany necklace for her wedding so this did feel a bit 
but fiancé pointed out maybe she was sending multiple charms with it too etc that she wants to create a special bracelet of our memories etc. I nodded and agreed still wanting to see the best in her. (got the wedding gift today it is a cinderella bracelet they well and two charms. still need to thank her for them... the heart says 'family forever and always')
there is part of me that just wants to stop making an effort by this point and I already told fiancé this is the last year I am sending them anything for Christmas. It feels mean and I feel like I am punishing the kids for her behaviour but I really feel like my kindness and understanding is being taken for granted by now. I really was desperate to remain close as I really have distanced myself from the rest of my family due to their selfish tendencies but I really am not sure how to feel about my cousin by this point.