I think if you are 18 and earning your own money you should contribute (if you live with your mom) a little to the household - simply that is what you do as an adult, you pay your rent/heating/electricity. Now your mom should be reasonable as knowing you earn little money. Ideally you would work out a reasonable amount of monthly rent to stay there and then she should not ask you for more.
That being said it should have nothing to do with her being laid off or being needy, etc.
YOu are 18 and have the option as an adult not to live with her.