People pleasers, people with poor boundaries, rescuers and people who let others walk all over them and then 'have a little cry' to themselves afterwards. People who don't think women should ever say no, especially not to a child. Oh and people who have no idea what severe trauma does to a person.
People also don't consider the whole picture. They can see the OP's close friend can't come if Louise doesn't and that a sad child is involved but are not considering the whole picture/wider context.
It's quite obvious that Julia shouldn't have asked this of the OP in the first place. It's her wedding day. It's not the time for charitable actions or putting yourself last. Not when she's organised a small wedding and with the reasons she gave in her OP.
Julia is likely a bit overwhelmed with the situation as I think any of us would be and is looking forward to the wedding/likely craving a bit of normality but it was incredibly rude to ask.
The fact she'd cleared it with everyone else first rather than getting the lie of the land from the OP first shows she knows its a big ask but was hoping the collective pressure would sway the OP's decision.
There is a thread running at the moment where someone has asked if they can take their husband and child to someone's hen do. Not for the actual thing even, just for a bit of a holiday that would be nice for them. The bride has similarly said no. And, the last time I looked, it was a unanimous YABU for asking response.
And this see thread where op brought her thrice not invited child to a wedding brunch and burst into public attention seeking tears at being told 'no!'
Hopefully, when things have settled down a bit, Julia will realise that she was wrong to have asked in the first place and understand exactly why the OP said no.
As much as anything, this girl has had her entire life turned upside down, is dealing with things that most people will never have any experience of. Spending a day with strangers at a wedding is unlikely to be the therapeutic experience Julia is hoping for. And she likely knows that herself. She just wants to go to the wedding and can't see any other way around it. Because there isn't one.
Most people in Julia's shoes would have contacted the OP and explained that she'd need to pull put of the wedding. The ball would then have been in the OP's court as to whether she extended an invitation to Louise or not.
I often read the BeKind responses and am glad I don't know those people in real life. There's being kind and then there's prostrating yourself at someone else's feet, inviting them to walk all over you and then, invariably, being upset about it afterwards.