Both I and a CPA told her a couple years ago to stop exposing herself to liability for his problems by filing seperately

Has her husband always been this way or it is a change in personality?

Filing jointly is a first step. She could still be liable for debts he is incurring. She should make an attempt to find out what is going on before filing for divorce.

She isn't signing documents that she isn't allowed to read?

My late brother-in-law had a similar personality and he left quite a mess. My sister-in-law signed documents she wasn't allowed to read. Their tax preparer (professional and paid) added to the mess with stupid tax mistakes. I thought they were committing deliberate tax fraud, but it was due to incompetence.

During this time the tax preparer also died in an accident. I talked to the person who was suppose to take over. After the first conversation, I would not let them talk to the IRS and had her move to a preparer who was competent. It took a couple of years to clean up the mess. Fortunately, with the tax preparer and BIL both deceased, the IRS didn't aggressively persue the situation. The IRS wasn't the only problem to be reseolved.