Advice for acruing interest on settlement deposit

I am concerned for a friend that had alot of money in her solicitors trust account for a deposit on her property, that took about 1 year to settle, that she has been ripped off by her solicitor as he did not give her the interest that accrued.
The deal has now settled. Does she have the ability to still claim that interest back now?? (IT was about $500,000 so yes, it is worth chasing!)