How soon is too soon?

Hi everyone, need some advice!
I was engaged in Nov 2021 with my partner of 6 years. Our wedding is on 20 July 2024. For background, our engagement had been quite long and we have had to postpone our wedding due to my health issues (I am now healthy but had a hard battle with cancer).

My FSIL just got engaged a few weeks ago with her partner of one year. She has tentatively scheduled her wedding date 6 weeks before mine. She is also my bridesmaid and I will be having my festivities in the month she is getting married. She knows all this information.
I personally think this is too close to my wedding and it will put me under unneccesary stress. There is no reason for her to not get married after us. I don't mind if she gets married earlier in the year before us. The fact that she is getting married before me is not the issue I have, I am anxious that I will be stressed and run down for my own wedding. I feel like this is selfish behaviour on her behalf.
WOULD LOVE YOUR ADVICE....FROM A STRESSED BRIDE!