I acted exactly this way with a friend and it caused massive issues between us.
What was happening was after lockdown I began having severe MH problems. My friend like you has also asked me to send a message saying at least that I'm having trouble and cant talk right now but even that felt like a struggle.
At the back of my mind is always the slight pressure that my friend will want a life update and will want to engage me in a conversation about her life and I dont feel up to the task. She will want to tell me about a guy she is dating, or her awesome new job - meanwhile I will need to tell her about the psych team at the hospital. That's impossible to explain to her though.
I feel even if I write telling her I'm going through a bad patch it doesnt change anything, she'll still be waiting for me to get back in touch to explain myself. It has caused arguments before. She may (like you) have felt hurt or confused by not having any sign of life. Equally though when she expresses what you do directly to me I then try to maintain the level of contact she wants and it ends up feeling like a part time job. Once she raised the issue with me our friendship never went back to the way it was before although I appreciate she wanted to get it off her chest.
I dont struggle this way with other friends who are more relaxed. Equally I have one friend who i know has also been through a bit of a tough time this year - normally it can be a few weeks or months for her to respond to me. I don't take it personally, just assume she has stuff going on. I send her a heart emoji or something every now and then to let her know shes on my mind but I dont try and engage her if you get me. I also dont expect her to justify absences - I assume she was depressed.
This was a massive ramble but I guess my point is we all see communicating through a different lens. To you two months seems an age. To me two months isnt that long when a lot of things have been going on? It's all about different personalities. One person is interpreted as selfish. The other is interpreted as harrassful.
The more time passes when you havent been in touch with a friend, the more stressful it is because you start thinking "fuck it has been TWO MONTHS". Yo realise you will need to explain and the longer you put it off the worse it gets - like a small fine building up the longer you ignore the letters.
What have your messages to her been like?