Bridesmaids - what to do??

Apologies for the slightly negative tone of this message. I’m getting married in April and have my sister as my MOH and niece as a junior bridesmaid. I wanted some friends in the bridal party so asked my close friend ‘M’. I also wanted to ask my other close friend ‘R’ but she has shown very little interest in my wedding (like zero). I’m quite a reserved person so didn’t want a fanfare, but a feeling of being happy for me would be nice. When I told my friends I was engaged all R kept saying was how jealous she was and how my engagement ring is the exact kind she would want. There was very little ‘congratulations’ or ‘I’m so happy for you’, it was all quite bitter (even my other friends noticed). To put this into prospective, I got engaged after being with my partner for 2 years. R has been with her boyfriend for 5/6 years and she is desperate for him to propose but he has no interest in getting married. I would love her to be my bridesmaid but not if it causes her any upset or if she is going to continue with the bitter tone, as it makes me feel quite awkward. I also think she’ll be upset if I have M as my bridesmaid and not her. It’s gotten quite complicated and im starting to regret asking M. Any advice would be great? Should I tell her how I feel?