Should I reply to this Happy Birthday message?

I wrote a very short version and a longer version with more details.
Short story: I’ve been completely ignored for months and now she wishes me happy birthday, “Hi, Happy Birthday to my bestie”. Wtf. Part of me doesn’t want to respond lol. What to do?

Long Story:
My “friend” has been ignoring me since last year, around October 2023. I’ve sent messages and stuff and she hardly ever responds, she’ll only react to the message. I’ll ask how she’s doing, How’s her new job etc and she would react (not reply) with a thumbs up emoji. Since January this she has completely ignored me, I sent messages, calls etc and I haven’t gotten a single reply nor reaction. I’m at a place in life where I detach from people easily so believe or not, her ignoring me made me feel as if a weight has been lifted off my chest, maybe cause she usually has a very heavy and negative outlook on life and hence an overall a heavy energy. But, at the beginning of it I did feel extremely hurt since I invest so much time with her and trying to help her just to receive this treatment. I give people their space, but I also think I deserve just a simple message back. Something as simple as “hey, I’m taking some space rn and won’t be chatting much” Will work for me. I’ve been worried SICK about her. But she’s okay and actually made some new friends , so I’m glad she’s alive and well. Anyways, she sent me that birthday message today ““Hi, Happy Birthday to my bestie”. I don’t even wanna reply, but I’ve been told not to drop to her level and ignore. What would you do in such a situation?
by the way: we’ve been friends for over 15 years. We didn’t have a falling out but she did give me attitude over a particular matter i advised her against. Maybe that’s why? If you want more details I’ll give in the comments.
Should I reply to this Happy Birthday message?
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