Mother in law has not given step granddaughter gift

My MIL bought, from a charity shop, a used plastic boat for her grandson. Under her Christmas tree was a huge pile of Christmas presents for her other grandchild. I have never forgotten and never will

This is so unkind; I think someone needs to speak to her. I can't get over the fact that she is prepared to upset a 5-year-old! Perhaps 'forgetting' MIL's birthday should be on the cards? Childish I agree, but then she is behaving childishly.FWIW I was a stepchild and my stepmother treated me as though I was hers, despite the fact that I was an adult when she married my dad. He wouldn't have married her if she had been mean to me.
I really think she needs to be told; the little girls should be loved for herself, not just because she is a 'blood' relative.

I know she hasn’t forgotten, she has spent the last 30 year's I’ve known her playing mind games, wanting a reaction, to the point we stayed out of her life for 5 years when my children were babies. But yes unkind is exactly what it is.

Is it at all possible she just forgot?

Otherwise, how unkind!! It saddens me so much how much stock some people put in “blood” relations only.

Angusann, how lovely to have welcomed another GC to the family, I say another because by the tone of your post you were already a Gran by way of your SGD.
In the shoes of the parents I personally would return the cheque, but that’s a call for the parents to make. I completely understand your hurt and anger at this sort of thing, if money was a factor as you say a wee minding like a pair of socks or a selection box would have been nice.
Would a fuss be the worst thing in the world to happen here? Ultimately as I say it’s up to the parents but I’m sure they’ll be grateful that you’re upset on behalf of your SGD and I’d encourage you to support them if they do choose to say anything regardless of any tantrums your MIL may have as a consequence!