If she was in a union, severance would be outlined in a collective bargaining agreement. I think most unions settle for 1 week per year of service - there's no fighting that.
Concerning using employment lawyers (non-union, non-contract employees), the first step would be to visit a few employment lawyer sites that have severance calculators. Their severance calculators give you a good idea as to what caselaw settlements are for your age, years of service, and position. Once you have a number in mind, try to negotiate yourself based on your findings before hiring a lawyer -- if you're successful, you'll end up with a lot more cash. If you can't come to an amicable agreement, employment lawyers work 2 ways: on retainer, about $400/hour. On contingency (they don't charge you until a settlement is reached) -- that costs about 25% of the settlement awarded to you.