So she gets upset and wants others to soothe her. It sounds like she never learned the basics of solving her own problems and easing her own worries or dealing with painful issues. She doesn't know how to handle painful feelings and looks outside to other people to deal with her pain.
She's worried and stressed about her husband losing his job and one less income , gets overwhelmed by the feelings, calls you to bring the kids over to ease her feelings and get her happiness fix. If it's not at an inconvenient time talk her through it or make suggestions she can do like taking a walk. But understand that seeing the children does make her happy and in and of itself is not a bad thing.
When it's inconvenient and she's using you guys as a pacifier, blankie, or lovey when she should be relying on her husband and you just can't accommodate the time it takes to soothe her and deal with her, find something else to do.
"I'm so sorry MIL, you caught me in the middle of nearly burning the chicken and rice but I'll call you back as soon as I have a free moment."
"I know you're having a rough time. I always take a nice hot soak in the tub and then take a walk. I wish I could stay on the phone and help you out some more, but someone is at the door and I think it's my neighbor."
"I'm so sorry you're feeling so upset right now. The kids and I will be around tomorrow for a visit as we already planned with you but we're expecting company in the next half hour. I'll have James call you after supper. In the meantime, take a hot bath and read a book. Talk to FIL and let him know how you're feeling. Gotta go... I think our company is here early!"