Child support in Canada

Long story short - the father basically paid $25k to a lawyer to avoid paying $10k in child support over x number of years, yep, that's him. Lowballed everything to the end... Right now he's paying an average of $300 per month for both kids. He's living in the lap of luxury and the mother is basically able to cover the cost of living only from paycheck to paycheck. She cannot afford to sue him - no money for it. The judge that presided over the divorce is no longer available and that was almost 3 years ago.

What other options are there in Canada? Is it as simple as talking to a lawyer to get back in front of a judge? She has the proof that his lifestyle far exceeds hers and her kids are suffering for it. Hoping a judge can look at the proof and do something to change/update the current court order.

Thanks.