Would you bother??

I would go up to 18... but what happened with her father's manners?

I stopped giving to my nephews after not being thanked.

My Boxing Day morning was writing thank you letters for my Christmas presents. No argument. I would not be inclined to give any gifts or money to someone who is rude enough to ignore me. Why have basic manners disappeared?

I quit after school age, if said kids can’t be bothered why should we. Been there with so many, they are more than capable of manners enough to say thank you. I have a very large family of nieces and nephews.

What do you mean.... she ignores you? Thats sounds awful.

No you are not being unreasonable and when you see her, say hello and if she ignores you then don't bother trying to communicate with her any further.

I would definitely stop when she is 18 and just send a card. You could stop this year but 18 is a good cut off point. I am doing that with great nieces and nephews. I felt a bit awkward at still sending to the younger ones only at first.

Maybe you might want to continue until her 18th birthday and stop then. ( You have come this far…).
But I gave up on my nephew long before that. Not even knowing if gifts had arrived, no thank you, not even a text.

The fact that she ignores you when you're there in person is the clincher for me. One could make allowances for teenage gaucheness if not for that. (I wouldn't involve her father in it at all.)