Her lawyer says she showed up 90 minutes prior - because that's what Air Canada suggests as a minimum.

Do you really think she did that and still missed her flight?

If so what was she doing?

There are tons of staff at an airport like VR or YZ all day, every day - clearly people were there to check her bag after a 5-10 minute lineup.

I bet in reality she got to the economy parking lot 90min  prior and took forever to get to the terminal or maybe was dropped off at the curb of the airport closer to an hour out... 3 kids, checked bags, too much carry-on, an oversized stroller, didn't know her way around the airport, maybe a diaper change... she set herself up for failure and only has herself to blame for missing a flight.

The airline did everything reasonable to accommodate her. 

Seats on the next flight - just have to sort sitting together out onboard because other people already have them.
Not happy?
A hotel and flight tomorrow then?
Still not happy?
What else would you expect?