@ITookABathWithAinsleyHarriott What a shitty thing to do! As I child I was thought that its rude to give a present to one person in the household and ignore the others. So maybe at 14 we could excuse this, but the 14 y.o was with the adult one, so the adult one could have bought a gift from both of them. NO EXCUSES!
My SD is not the most thoughtful girl out there. I only see her EOW or less and I no longer have the opportunity to do much for her. Her mother doesnt like me, my DH doesnt care about gifts, so I was also hurt seeing her buying gifts for her family or friends (after getting a nice Xmas and bday gift from me) or congratulating her mothers boyfriend with fathers day, but forgetting congratulating me with mothers day (and Ive known her longer and took care of her when she was younger and was coming more often).
But as of 16, she surprised me with bringing me token gifts from her trips and last Xmas, and she just texted me to say that she has a fun gift for us (I guess one for the family, but she doesnt work, so its a nice thought). I know that nobody promted her.
So in your case, when you do even more for them than I do, its clearly selfishness. So I would also not get her a gift for her bday (what a nerve she has to send you links to expensive gifts for herself!). I dont believe in giving and giving and just hoping that one day the person starts appreciating it by themselves. Sometimes there should be consequences and if they continue not caring, at least it hurts less. My adult step sons dont congratulate me with my bday (or any other day), I stopped doing it too. They want us to be like strangers, let be it.