Sick kid on his dads weekend

I need some advice and I need to see if maybe my thought process is on par…

Around 2pm yesterday my boyfriend’s ex wife gets a call from her sons school and he is throwing up. Basically he finishes out the school day.
It is our weekend to get his son.
She doesn’t tell us until I pick him up of the situation.
So we have a sick kid who is throwing up and is running a fever.
Is she in the wrong for not telling us sooner, should she have cancelled his weekend with his dad?

She does this A LOT and personally I think she is a selfish parent… let me explain
In 2020 when Covid first started she sent him to us when she was in quarantine for being within 6 feet of someone who had Covid, which meant she had a high risk for catching Covid she did NOT tell us she was in quarantine, I got Covid due to this (I have a weakened immune system) her son was supposed to quarantine with us for 2 weeks according to the health department and she insisted he come home immediately even though he had been exposed, she took him to the DR for a physical and lied about his Covid exposure.
Fast forward to a few weeks ago, everyone in their house was sick, fevers, runny noses etc. Well they all tested positive for Covid and before they were tested she sent her son here for the weekend where we (my boyfriend and I) contracted Covid as well.
Am I wrong for thinking when the boyfriends son is sick he should stay home until he is well, or am I the a**hole for thinking the boyfriends ex wife is selfish and that she does this on purpose so she doesn’t have to deal with a sick kid?

We get him A LOT we get him during the week and sometimes every weekend just as a reference