How do I kindly end a friendship with someone who can’t take a hint?

I (29f) was recently reached out to by someone who was a close friend of mine when we were in medical school. I’ll call her Megan (28f). Megan and I met during the first semester of med school, she was really confident and bubbly and invited me to go to a workout class with her. I’m a little shy and it takes me longer to make friends, but I’ve always loved attaching myself to an extrovert because they do most of the work for me re- finding friend groups to hang with and events to go to.

Anyways, Megan and I started hanging out first semester. I was working on establishing a couple other friendships as well, but not really close with anyone else yet. After spring break, the pandemic hit and we never went back to regular classes. It became near impossible to make new friends at that point.

Medical school is not something you can get through alone. I clung to Megan as my only close classmate. We studied together, attended online class together, drank wine and commiserated together…. You get the idea. She was my partner in the trenches, and we became close friends. I helped her through a break up and she helped me though hard times too.

I was a really good friend to Megan, but when we graduated and began our careers, she took a job out of state. And honestly, I was relieved. Despite being a good partner through school, Megan was an extremely high maintenance friend. She would send dozens of texts at once and call repeatedly if I didn’t respond. She could be childish and self-centered. She had the diet of a 12 year old (literally only ate chicken nuggets and Mac and cheese), and got angry when people didn’t shower her with enough gifts and compliments on her birthday.

I tried to let the friendship fizzle out. I would take really long breaks between responding to her texts and calls. I never tried to visit her and I didn’t really reach out to her. I wanted to set expectations for our long distance friendship. I think fondly of our time together and I’d like to stay in touch by liking each other’s posts and commenting on big life events on Instagram. But outside of that, I do not want a friendship with this girl.

She got engaged recently and called me for the first time in about 6 months, I didn’t answer so she sent a text requesting to schedule a call. I didn’t reply, but she followed up the next day.

I’m terrified that she’s going to ask me to be in her wedding, and I cannot say yes to that request you guys. I don’t even want to attend as a guest. I am so broke right now! I’m filled with dread at the idea of calling her back, but I really don’t want to ghost her or hurt her feelings by being honest. She has never wronged me or hurt me, and we got each other through a really tough few years. I still haven’t responded yet. What should I do??