is my mom responsible for her husband's medical bills?

[mymomsPOA]

What is the name of your state (only U.S. law)? NJ

My mother and her husband are each in separate nursing homes. They both have dementia and I am my mom's POA.
Each month $ it taken from my mom's small pension to pay for her husband's medical insurance. Each month my mom is reimbursed the $ for his medical insurance from the nursing home who gets my step-father's social security/disability $. He's currently on Medicaid. he has been hospitalized 3 or 4 times and the insurance has covered most of it, and i assume medicaid is picking up the rest because i have not been asked to fork up any $.
My step-father's POA is his sister and I work with her to get the reimbursement for the medical insurance that my mother pays for her husband. I am questioning whether paying this ins and getting reimbursed each month is worth the hassle and i brought this up to my step-father's sister. This was her response: "if medical bills are not covered by medicaid or insurance, then your mother, as his spouse would be held responsible".
My questions are 1) if he's on medicaid doesn't medicaid cover all his medical bills? i understand some doctors do not "take" medicaid but if they work on him and then find out he's on medicaid, whose fault is that? shouldn't they just have to eat it if they didn't find out he was on medicaid before they provided their service? 2) would my mother be held responsible for his medical bills? the research i have found on this is mixed.

[Kiawah]

My questions are 1) if he's on medicaid doesn't medicaid cover all his medical bills?

In my MIL's case, who is on medicaid...it does not cover all of her bill's, but the combination of medicaid and her secondary insurance does. Well it is probably more appropriate to say that at least in the past, everything has been covered.

2) would my mother be held responsible for his medical bills? the research i have found on this is mixed.

How are the assets titled? House, bank accounts, etc

[mymomsPOA]

there's no house or other assets. his 401K is gone to pay his nursing home, hence the medicaid. she's got a 401K in her name but it's being used up to pay for her assisted living. That will be gone soon and she too will be on medicaid.