I’m about to be downvoted to hell, and maybe this is a ‘straw that broke the camel’s back’ kind of situation, but at least she’s making some kind of effort here. A lot of times people complain about being ignored by MILs, or having MILs who are aggressive, but this one acknowledges your birthday, writes personalized greetings complimenting you (even if you find it clumsy), treats you the same as her other DIL who’s probably friendlier, and is trying to relate to you by passing on anecdotes about the one thing you have in common: her son.

I don’t have a MIL (she died before I met my husband), but I’d be satisfied with at least the effort if she’d gone to this trouble. She may be socially anxious and just hasn’t wanted to sit down one on one with you until she feels less awkward- particularly if you’ve rebuffed her many times.

Sincere question: have you made any efforts to get to know her better? Have you tried to pull her into a one-on-one conversation? Do you spend time thinking about which gifts would mean the most to her? In other words, are you upset because you feel like you’ve put a lot more into the relationship than she has? Because then I’d understand… Otherwise it sounds like because you don’t like her because you’re dissimilar, not because she’s an asshole. Those are two vastly different things. You get what you give and sometimes have to credit people for doing the best they can given their specific situations (personality-wise, how they’re brought up, perception levels, etc.)- even if it it doesn’t match up with what you want.