To ask my SIL to not bring her “therapy dog” to our family BBQ?

Nope. She’s so ‘anxious’ that she doesn’t give a shit about upsetting other people with her unruly dog and guilt tripping you… I call attention seeking bullshit. Don’t pander to it.

At the same time, I agree with the pp who mentioned you need to be careful as this is your dh family. Can he not have a word with her about the dogs previous behaviour and set expectations that way?

Could dh manage her and the dog? Just with her being SIL and him not seeing the problem it can come across as though you don't care about your in-laws

Can she just keep it on a lead or tethered next to her, or even crated so it can't steal food or knock over children?

You're not being unreasonable but is there any compromise like dog needs to stay on a short lead or dog can stay in the garage or anything?

Spaniels need a lot of training and a clear outlet for energy or they can get really naughty/mischievous. It sounds like she's not doing enough with hers and hasn't trained it properly which is a shame because they're really biddable dogs who are eager to please. I would also worry about a spaniel bounding about around toddlers- they might not be remotely aggressive but it's easy for them to knock a child over if they aren't careful.

Your sil needs to train her dog properly is the key issue here if she wants it to be welcome wherever she goes. And even then without proper registration as a service animal places and people will still be entitled to decline her.

She sounds quite full on and absorbed herself to be honest if she can't see why someone wouldn't want her dog at a party when it behaves in that way.

I think you have to be careful excluding your husbands sister when he doesn’t think
you should, regardless of that fact you’re not being unreasonable in not wanting this at your bbq.

Is it your dh’s sister or your brothers wife? If your dh thinks you’re being rigid and it’s his sister I think you should let her come but send her a message saying you expect the dog to be on a short lead at all times and away from food. Maybe if her dog impacts on her day suddenly taking it everywhere may not be as attractive.

Here to vocalise my support for Zero Tolerance for Shit Dog Owners

It's certainly not alright for the dog to be allowed to chase children and steal food. At the very least the dog should be kept under control.
I would suggest a compromise whereby the dog comes but is kept on a lead. Too bad if SIL can't agree - your house, your rules.

She's taking the p* with calling this dog a therapy dog when it's not actually trained to be quiet, sit and look angelic etc.
My dog bless his soul who had springer in his mix could smell migraines 12 hours before I got symptoms. I could - theoretically - say he is my medical alert dog and must come everywhere etc. I didn't do. While he was capable of being bouncy and doolally dip, he also knew his manners. If it was appropriate, he would come along. If not, he stayed at home.
Stand firm and make it clear that it's the dog's behaviour that is the issue. If he can settle down then he'll be welcome - without needing a therapy dog label.

“So sorry, it’s difficult managing conflicting needs, with the toddlers etc. we’ll see you at next summer’s BBQ when he has learned not to be a sausage monster xx”

She has anxiety? Fine… but the way she carries on puts a huge burden on others. If she wants a ‘therapy dog’ it needs to be trained and behave like a service dog.

YANBU. I think she lost any sympathy when she tried the “disrespecting mental health card”. If she doesn’t want to come without the dog, that’s fine. Suggest we takes the dog to training classes and once it becomes better trained/behaved, it will be welcome but not until then. Part of being a good dog owner is being a responsible and considerate one and it seems she isn’t. No doubt that’s due to her mental health too. 😜

I’m with you on this, 3 toddlers, bbq, food laid out, badly behaved, untrained dog… nah. As above I’d say to her “ok, see you another time then.”

“Aw that’s a shame it would have been lovely to see you”

done.

Cool she's solved the problem for you by saying she's not coming. Just say you'll catch up at another time and don't give the situation any more attention, people like this love the drama.

Just text her sorry you won't see her this time. Hope to see her soon....