Ugh so SIL issue. What to do?

My SIL rang up her cell bill to a point of not being able to pay for the 3rd time . Well my MIL was on her plan and had asked that she be put on ours . So I set it up and got her the exact same iPhone. Well my MIL didn't factory seep the phone before giving it to her daughter . And he'll broke loose.

My SIL read through her moms private fb messages to me and who probably everyone else instead of just logging out and respecting privacy.

Now my SIL is crying martyrdom because we "talk behind her back". Now in my brain the logic is what I say to someone else is private.

Now she's on a rant🙄 to protect her middle school aged kids .

The family has been walking on eggshells since her eldest enlisted in the marines this past August.

I'm dying for her to really ask my opinion of her .

her house hardly ever has food but there's always an 18pack of beer

she's been lucky having a job that's an "insult to her intelligence" but calls out because she's hung over and can't function

She's forever asking someone for money toll her husbands next pay.

Basically she's a semi functioning alcoholic and her husband is too afraid to stir trouble.

I apologized to my husband for his sister being snoopy and looking for dirt and this causing issues with their dynamic. Then I told him if I couldn't be around her kids to not feel inclined to not have a relationship whit them, but have a relationship and I am fine with being left out. Her eldest had said before leaving for boot that he wanted to move in with us afterwards ... not sure how that will go.

Idk what else to do. It's too tiresome to tiptoe around a pariah