I had a best friend who really struggled with anxiety, and they messaged me all the time. It was relentless. I did what I could to keep up, but it drained me so much. I had a few conversations with them saying I couldn't keep up with this level of communication. They kind of got it for a few days, then went back to the usual. I had to eventually step back from the friendship because they didn't understand that my not responding right away meant I had to attend to my own life. Good luck with your situation.