First, before the accident occurred, the trade union would have negotiated benefit packages including good compensation for short and long term disability coverage.
Next, the union would help her negotiate any necessary leaves, compensation, and accommodations necessary as a result of the accident. Often workers are uncomfortable with asking for these things and concerned about negative career consequences. The union would help inform her of her rights and negotiate on her behalf.
The union would provide legal aid if needed.
Finally, as a unionized employee, she would be at less risk of unfair dismissal if she became partially disabled or needed to take time off to recover from her injury.