My wife's mother moved in two years ago, she is filling up her bedroom and bathroom with so much stuff there's almost no room left. Help?

Mom-in-law moved in with us last year because she desparately needed back surgery, and could no longer live at home with her diabetic husband. Now she has recovered. She is essentially normal mentally, in her early seventies, but has limited mobility due to several fused vertebrae, substantial arthritis, and osteoporosis.

She continually shops at places like Walmart and online stores, even though she has covered nearly everything in her bedroom and bathroom with stuff. She gets several magazines a week, and collects items normally considered worthless like paper cups and plastic soft drink bottles. A stack of empty boxes reaches the ceiling, and another stack is growing taller by the week.

Even her bed is almost completely covered, there is just enough room for her to lay on her side. We have to nag her to let us change her bed linens, and then it takes her hours to make it possible. She's using disposable pads on her bed as a stopgap. She has limited mobility, and can just barely navigate the mess.

My wife and I are the homeowners, and are becoming increasingly frustrated. Mom-in-law is outwardly oblivious to the problem, and frequently shows us the latest bargains she has discovered. She even buys stuff for us, often inexpensive and redundant. We are trying to simplify our lives and remove old stuff that we have collected, so this is the opposite of helpful.

We recently emptied a large closet and offered it to her. We included plastic containers to help carry and organize her stuff. She hasn't even opened its door.

She used her bathroom shower curtain rod for hanging clothes, until there was so much clothing it pulled the bar off the walls. I had to shift shoes and clothing to get close enough to re-hang it. She has fallen in her room more than once, but she claims it is because she lost her balance; not because she stumbled over the obstacles littering the floor.

This year she decided she would rather eat most of her meals sitting on the edge of her bed. She does not see well enough to do this neatly, and can not easily reach down to the floor. She keeps containers of snack foods in her room now, and treats to feed our cats.

We have considered moving her to an assisted living facility, but she can't afford it an neither can we. That would cost over $3500 per month in our area. We both work full time plus, but do not want to spend our retirement money financing hers. She pays a modest amount towards our expenses each month. She would like to move back with her husband, where they lived with this kind of mess for many years. But he was recently diagnosed with congestive heart failure and does not seem to be doing well. He's very private and rarely talks to any of his children.

So what to do? Do we invade what has been "her space" in our home, and attempt to organize her belongings? That seems dramatic and risky, but what other options are there?

So far we have only done this on a small scale - removing obvious trash, vacuuming the floor space we can reach. Would interfering to a much greater extent open us to accusations of elder abuse? Theft? We do not know whether she would physically resist such an intervention. Every time we even hint at the topic, she becomes very evasive and dismissive.

I have read a lot about people who are compulsive "collectors", and have found no effective solution. Most of those are people doing it in their own homes - not their daughter and son in law's!

Has anyone found a good way to handle this? What are the steps?