Close friend avoided all my wedding activities

Hi all! I want some opinions. I’ve had a close friend for 6-7 years I’ve kept touch with almost every week. We were really close when we lived in the same state, and remained close even when I moved a few hours away. When I got engaged, my fiancé and I even made a point to visit the day after we got engaged to celebrate. I asked her to be a bridesmaid (or a reader) a few months later, and she awkwardly turned this down saying she didn’t want to feel excluded from the group being out of state. I brushed it off not really understanding that reasoning but respected it. When bachelorette emails started circling to gain interest, she avoided contacting my sister back and never responded until I texted her she hadn’t responded yet, and she said she was really suffering from social outings and didn’t want to go. I understood. For my bridal shower, she never mentioned to me she couldn’t come, and also did not RSVP to my sister again. She sent a small gift a few weeks later, and I called her saying thank you, we caught up, and that same phone call she mentioned she was having trouble finding doggy care for the wedding (2.5 months to wedding. We sent save the dates 10 months before our wedding)


I didn’t hear anything else aside us catching up like normal until the week of RSVPs, I asked her to kindly mail us hers by the deadline in 4 days, and her response was “it’s on my list to mail” and she was asking if I was getting excited. Which I assumed she was coming until I got the rsvp in the mail on the deadline and it was a NO with saying they couldn’t find dog care. I texted her a few days later just saying I was disappointed she didn’t want to call me to tell me up front. Come wedding day, I got several texts from friends saying they were thinking of me but never heard from her before or after until we got a congrats card in the mail a week later.
I’m still confused how she is choose not to communicate, and my now husband thinks it’s not worth my energy. It truly sounds like she has social anxiety but the behavior of just avoiding things at my and my sisters expense, I thought we were closer than that. I’d like your take on this, I’m an extremely empathetic friend who is often very relatable and I am “that friend” who is super understanding that my friends come to for advice, but this one I just can’t wrap my head around. I’m not a bridezilla and I do believe this is more around how she thinks avoiding communicating is the answer.