Is this messed up? What to do?

I think that your grandmother is being very selfish first of all writing that type of letter knowing that your parents needed to borrow the money to repair break pads on the car and rather complacent in her way of thinking,because in my opinion it seems as though she is definitely blaming your mother for her having to or being forced into a marriage with your grandfather just because she had gotten herself pregnant with your mom "which is ludicrous" and is ultimately taking it out on you and the rest of your family for no apparent reason at all.I think that also she is just trying to save face for the fact that she feels a sense of responsibility or obligation "as a grandmother" to send out birthday cards even though her intention it sounds as though is a selfish motivated one so in all honesty i think that you and your family have nothing to lose in this situation,because she obviously does not care enough as to whether or not she has any contact with you and your family so my advice would be to limit all contact with her if that is the type of individual she really is because this is so not worth the aggravation.

I think your, Grandmother, needs to talk to a mental health Doctor. She has some deep anger issues that should have been addressed years ago. No offense.

your grandmother sounds nasty, no offense. still mad at your mom for being born? kind of late for that, she's already been born and that's a dumb reason to hate someone. but I guess she still sends you the birthday cars because her husband or someone else tells her she should at least do that? or maybe she still feels obligated to somehow Idk.

Grandma needs professional help

Your grandma sounds messed up.

I think your grandma has issues.