looks like someone won't seeing the grankid

Her instantly angry reaction at not getting a material gift right away is a huge red flag. I'd seriously consider whether you want this extremely entitled self-centered person in your lives.

All these commenters stating that OP shouldn’t have done that and given the Mother a present - I hope you aren’t or won’t be parents. Typical materialism. You should be ashamed. This Mother is a POS.

Well, you already know she won't appreciate the kiddo, so deny her access, maybe? Remember, she may change her tune, but not so much her stripes, possibly.

Dude, that isn't a birthday present. At least get some flowers and a card!

I think it would have been better if there was an actual present, even if it was something small and not related to the real deal. By doing so, you can then tell her that the real deal is coming next spring, so that way, your surprise will still be safe and she will be looking forward to it.

She sounds like a real charmer.