First I'm NOT a doctor, but a computer programmer and I look at logical first.
Try googling CBD and seizures, From that, I would suggest, maybe let's try something else other than cbds and eliminate THCs (if she is getting this elsewhere) which everyone thinks is the cure all for our stressful lives. When did your brother start having seizures, same time he started to use CBDs?? Look at the inputs and see if they result in the output of seizures. Kind of like machine learning, but unfortunately we don't get to see every possible inputs. We can look at inputs outside of the normal people usage though. (Meaning do I "eat more cornflakes" more than normal than other people - where cornflakes filled in with all inputs of your daughters daily life, it doesn't even have to be through the digestive system, could be walk 3 miles around the manufacturing plant near the house everyday......)

At top of my Google Search "does CBD cause seizures" (of course you will fine equally that it also stopes seizures) but research what you can, and take everything you read with a grain of salt.

She needs to look back and see if she bumped up her CBD usage before her first seizure. Then did stress cause even more usage of CBDs due to diagnosis to cause the second.

Google Search "does CBD cause seizures" -- In a 2020 study, researchers found that patients taking a commercial CBD product had a 70 percent increase in seizures, whereas the group taking prescription CBD had a 39 percent reduction. A reason for this may be that the commercial CBD products had higher levels of THC, which can be a trigger for seizures" -- Strange looks like no matter uncontrolled usage or through RX it still increases chance of seizures.