I know this is not a life or death issue but...
My 3 years ex gf broke up with me 3 months ago, since then I have moved on quite well, with up and downs.
She recently contacted me to wish me a happy birthday, hoped everything was going well etc etc, but with no questions or anything. This was 4 days after my birthday and she said she had been really busy and thats why she didn't remember. I just answered to the text something like "Thank you

" I thought that answering simply was the best thing to do?
Her birthday is in a couple of weeks. I don't have any expectations or anything, but I think it wouldn't hurt me to act the best way possible to make her feel interested or something.
Should I tell her something simple to wish her a happy birthday? maybe the next day. Or just ignore it completely?
I know it doesn't make a lot of sense, I am not trying to get her back cos it's pointless but It would definitely make me feel good if it gets her thinking...
Thank you!