I've been friends with Emily (not her real name!), for years. We see a lot of each other and get on really well.
We've always bought birthday presents for each other, but she never thanks me properly for them! It seems to happen that we get together in the week leading up to her birthday, and I'll take her (wrapped) present with me. She'll say something like 'Ooh thank you so much, I'll save that to open on Sunday!' (or whenever her birthday is). Then she never mentions it again! I'll always send a follow-up text after my birthday, 'Thank you so much for my (whatever), I love it, etc'. But she never does.
I felt a bit miffed about her birthday last week. I called round with her present (on the off-chance she'd be in). She wasn't, she was out for a family meal, but no problem, I left her gift bag by her front door (covered over), texted Happy Birthday, and said it was there.
She replied next morning, 'Thank you for my gift bag, it was outside my door when I got back, are you still coming on Friday? x'
This was a meet-up for birthday drinks with a few other friends too. I went along, had a lovely time, but she didn't mention her present!
Tbh if I just wrapped up a random box of chocs I happened to have in the house I wouldn't mind, but I always put thought into presents for people, and had gone shopping especially to get this, (a lovely scented candle and set of mini gin & tonics with a glass).
She may think she's thanked me (by saying she's received it) but she hasn't really, surely? She buys me equally nice presents, so it's not as if she doesn't 'do birthdays'!