I personally don't think it's a good idea myself. I've actually been to the hospital twice, and each time I came out wondering, quite honestly, just how many other people go home and take their lives after such a prison-like, and rather demeaning experience.
My experience was much like your Mum's, although I wasn't in the hospital long. While I was there, however, I spent most of my time alone as other people with various problems walked about, waiting for the hospital staff to give them their next dose of whatever the doctor saw fit. Sometimes this monotony was broken up by random people taking you into rooms and making you undress completely to make sure you didn't have anything you could harm yourself with. Or people's families would visit and smile their fake smiles as their institutionalized relatives sat there in a drugged up haze claiming that things would be different when they came home. Or sometimes people would even get angry and cause a commotion that left the whole place imbalanced and reminded me that I was indeed surrounded by at least a few people who were severely mentally ill.
There were group sessions but they were more comparable to alcoholic anonymous meetings than anything else, and I found it hard to relate to anyone.
My Dad doesn't want me to go to the hospital for my safety, but to help me get over my anxiety so that I can function in the outside world. But I know that going to one of those places again won't help me. He won't listen, though. He's convinced that me being committed to such a place is the only real solution to my problems. But because these places don't even come close to specializing in treating people with social anxiety I know it'd be a waste of time and money. I'd be ignored and my condition would be trivialized just as it had been in the past. I suppose I'd have to add alcoholism or drug-addiction to be worthy of people's attention.
During one of my short stays in the hospital I had to be in a group with about 6 or 7 other young people and we sat in this cramped, hot room with two counselors. One of them was a pregnant woman who seemed to have a rather cold personality. The way she would eye us made it so uncomfortable for me. At one point I broke out in a cold sweat and was a nervous wreck, but no one else in the room understood what I was going through in the least. One guy, a relapsing drug-addicted teenager, even voiced his opinion about how pointless the group was because we were all going through different things and he didn't understand my anxiety because the rest of them had never experienced it. We were just a group of people with various ailments sitting in a room struggling to express our feelings towards one another until the doctor said we could return to our normal lives. The whole experience sent my faith in the mental health system down the tube, although I went to therapy a lot afterwards.
You're right about being sectioned being like jail. It is very similar. In fact, the last time I went to the hospital I forced to ride in the back of a police car. If anything, going to the hospital probably made things worse.