To tell sil she's being out of order?

[lalalalafunk]

About to meet sil for a walk as she needs to talk.

She just sent me this text-

Xxxx's been really pissing me off lately. I have an ultrasound next week that he likely won't be able to go to because he'll have to be with Xxxx (her ds aged 16 months). I'm considering refusing to tell him the gender if they can determine it. Too mean or acceptable?

She's got form for stuff like this. Her daughter was quite ill a while back and she hid it from him and refused to tell him anything as he'd annoyed her that day.

I feel like I should tell her this is not ok.

No matter how annoyed I get with dh (and believe me I do sometimes ) I never use ds against him. It just feel like something sacred you don't do.

Should I keep my beak out and say 'up to you' or set her straight kindly?

Name changed for this btw.

[ohtheholidays]

Is there anyone else that can look after they're DS so they can both go to the scan?

With the rest of her childish and selfish behavior I don't know what to suggest but she might want to be careful there's only so much pushing anyone can be expected to put up with before they walk.