NC for this. Not sure if this is more of a WWYD or possibly just a rant!
It's DS's birthday on Friday and we're having a little party in our house on Saturday. There will be about 20 adults and ten children from 1-8.
SIL doesn't have any children, quite often makes a point of saying she doesn't want any, but has two dogs. She text DH last night to see if we needed her to bring anything and DH asked if she could pick a cake up from Costco on the way to save us doing it on Friday. She replied saying that she wouldn't have room in the car for the cake with the dogs being in there.
DH replied asking why the dogs would be in the car and she replied saying that she wouldn't be able to leave them at home for the few hours she is out at the party.
DH ended up calling her up and telling her that the dogs wouldn't be able to come, she then went on to say how the weekend is her time with the dogs and she doesn't want to leave them. She also knows that we've recently had our garden done and so said it would be really nice for them to be able to play outside. He just repeated that the dogs weren't able to come as we are possibly getting a bouncy castle on the day(our friend owns one and can give it to us last minute) if the weather is ok. She accused him of making this up and that he should have made it clear the invite wasn't for the whole family before saying that if her dogs went welcome then she wouldn't be comings do then hung up. DH was just in shock and we couldn't think of anything else to say to her. If she wants to miss her nephews first birthday because she can't leave the dogs for four hours at the most despite leaving them from half seven to half seven every day at work then it's up to her.
She text me earlier to ask if DH had told me what she had said. I replied and said he had and that it was a shame for her to miss the party but the dogs can't come and we had assumed that she would have known that. She replied saying it was a shame that we didn't recognise that the dogs are part of her family. I said that I know she cares about her dogs but this is a child's party and we don't want them here for it. She has just replied with this text
"I feel like you don't realise how important they are to me. They are my family, my babies. I would never not invite DS to my house or say he wasn't welcome or suggest you leave him at home or with a sitter. I'm not going to come on Saturday. I haven't seen DSsince Christmas and was looking forward to it but it's unfair to ask me to give up time with the boys when I get to spend so little time with them as it is."
I am sat here just in disbelief. I don't even know what to say to her.
I know I'm not being unreasonable not inviting the dogs to my house. I just have no idea where to go with this now. DH is in a meeting until one so I can't even call him to tell him what's been said. My jaw is aching from my face just being like this 
for the last ten minutes! She's always been very precious about the dogs and didn't come to a Christmas Eve thing at our old flat because we didn't have space for the dogs and all the presents were out under the tree etc. But I thought she would be a bit more reasonable about leaving them for a few hours to see DS.
Does anyone have any advice please?!