Depending on the very precise facts of the incident, her actions could be considered to be the primary cause of the accident. In fact it appears she likely is the primary cause of the accident.
And how does your wife know the guy didn’t try to slow down? Maybe he did but even that was not enough to avoid hitting somebody that,just pulled out in front of them and had to take further action to avoid a Collision?
Neither attorneys nor insurance companies make a legal determination of fault or percentage of fault. They make claims. Unless a court agrees with the claim, it doesn’t hold any weight.
Reprrt this to your imsurance company and don’t talk to anybody but your insurance company about this for the time being.

