Why did she delete her comment on Facebook?

So me and this girl had a fight in March where she called me a snake because I was talking to her friend about her and bad things she did. She ended the conversation by saying “Don’t ever say nothing to me for as long as I live”. So I did just that we stopped talking. So my birthday was 2 days ago and Facebook notified me when she wrote happy birthday on my wall. But when I checked my wall post the next day I noticed she deleted her comment. Why did she deleted her comment and why did it take her nearly 3 months to delete me out of her phone???