Friend is mad at me

I posted about this before but the situation has developed since then. Long story short, a close friend of mine who is 10 years older than me (we met in college) asked me to her graduation party. I told her I couldn't go because I didn't feel comfortable going with tons of people and she's immunocompromised so if I was a carrier of COVID it would be a risk to her. Also I was going to see my partner who I rarely get to spend alone time with as is. I apologized. I told her I would celebrate with her another way. This was over text.

Usually this friend texts me every few days, but she hasn't texted me at all since. I asked her how she was doing, no reply, left on read. She keeps posting on Fb about how she feels hurt and confused and idk if it's my fault, but frankly I'm starting not to care. If she is mad, I thought she would be more mature than this and willing to tell me directly. I think I had a valid reason for not attending her party. If she isn't mad, I don't know why she would be acting this way. Even when she is very busy she keeps in touch. I have been a very good friend up to this point and I don't think I deserve to be ignored. Can someone give me advice on what to do?