Yeah, one of my so-called best friends didn't acknowledge my birthday this year - it's in the early Spring. It's always me getting in touch and tbh I am sick of it. (We meet every 2 months normally, and she never contacts me first as she is always sooooo very very busy.) 🙄
After I contacted her to meet up before Christmas (mid December last year,) I didn't contact her again. My birthday came and went (early Spring) and nothing... Not even a text. Then 2 weeks after my birthday she sent a Facebook message saying 'sorry I missed your birthday, I have just been so busy! I have had sooooo much on! I will make it up to you! Let's meet soon.' (Too busy to send a 2 word text: HAPPY BIRTHDAY! Really?') 
But she never said when she could meet. So then it was down to me AGAIN to arrange it! 
Also, every time I said 'hey, when shall we meet?' she messages back after 2-3 DAYS and say 'I'll have to let you know, I am a bit busy lately.' (She's always very 'busy!') 🙄 Then about 5-6 days after I message her, I get a date out of her.
Anyway, this year, we eventually met a MONTH after my birthday and she gave me a Christmas Gift Set of smellies. Clearly regifted, as she hadn't just bought it - because it was 4-5 months after Christmas.
She didn't 'make anything up to me' at all. 
It was her birthday in August and I contacted her, (again!) and met up with her and gave her a couple of gifts. But I have not seen her since or heard from her. I'm secretly hoping she doesn't get in touch. I CBA with her. We normally meet in mid December. If by some miracle she does contact me, I might say I've got covid or something. CBA!
She is not poorly or anything, she is just always sooooooooo busy. No-one is as busy as her! 🙄