Unfortunately, our "spidey" senses are usually right, the old "looks like a duck. walks like a duck, quacks like a duck" thing. You need to ask yourself if you really want to jump into this again. Your sis seems to have a line with your mom. Maybe it's time to let your mom deal with her. You know what she's like when she's wasted and you CAN'T DO ANYTHING ABOUT IT. She's either got to crash and burn or get unstuck off of stupid.
Suboxone withdrawal can get real bad if she takes specific other meds to counteract what's going on physically. NO BENZO's, that's xanax or any generic form of benzo, lorazapam, alprazolam, clonozapam, etc.
She's looking at 7-10 days of withdrawal. It's going to suck, she will be depressed, her opiate receptors are gonna be whacked, she's going to be sicker than a dog, and other than a chemical detox, that takes about 24 hours, she's going to have to bite the bullet. Some Dr.s' give valium, but that can be abused and they're just as messed up as when they started detoxing.
She's really setting herself up for failure by NOT slowly weaning herself off. That's what addicts do, they throw a monkey wrench into their "program", and it's back to heroin.
The biggest problem is heroin is cheap. A junkie can maintain on $45/day vs. $800/day back in the 70's-early 80's, but the stuff is a lot more pure, dangerously pure. Suboxone is easy to find on the street, just like benzo's, because they take the edge off when junkies are strung out.
Your sis has the "tools" to get clean. She doesn't need someone to hold her hand or kick her butt. You need to think of yourself, your children, and your husband. What can YOU handle? How much "drama" can you allow into your life?
You sound like a "fixer"....I was too. I totally disregarded my own issues to jump in and help someone else. It made my issues worse. Nobody is worth getting to the point that your depression drives you 2 seconds away from cashing it in, because you didn't put yourself first.
Sounds cold, but we have to save ourselves before we even contemplate helping others.
My advise? Back away from your sis. She's an adult, and relapse is so common, you want to punch a doc for even giving that glimmer of recovery. NOTHING is going to help her until she decides to do it the right way. Do NOT give her any of your meds. The best thing you can do is make it hard on her.
She made the choice to stop the Suboxone, she is going to feel like she's at death's door, she's going to have to suck it up for 7-10 days.
Do NOT let her suck you into it. Let mom handle it.
From what you've posted in the last months, you need to take care of YOU.
Addiction sucks, and it does a pretty good job of destroying everyone connected to the addict. Cherish the times sis is sober, but distance yourself when she gets sucked back in.
I haven't seen or talked to my daughter, or my 3 grandchildren since 2005. What she put me through was hell, my metal health tanked and the stress gave my BF 3 heart attacks (he had knee surgery and we get a frantic call that
we needed to be 2 hours away at a CPS hearing for my daughter the next day, tissue from the surgery migrated to his heart and closed an artery 95%, air evac to Heart Hospital in Phoenix, stint in heart, etc, etc.) To say nothing of a $1500 charge she put on my credit card during that time, it's all a long story and total BS.
TAKE CARE OF YOURSELF!
!
I finally put her out of my life for a bit and then got her on Intervention and she's been doing well (for the most part) ever since. 
