I would buy her one. Either way, she may make a comment. However, being unhappy about you doing the right thing is better than being unhappy over doing the wrong thing.
I work with my estranged spouse and he didn't even acknowledge my birthday last September. The other employees did, so there's no way he forgot! It still hurts me deeply.
M: ten years BS23, BS17 Step-SS20, SS16, SS14 Separated: August 07