Marriage takes lots of work and communication, as you know! Right now,it sounds like HONEST communication is really lacking on both parts.
There are a lot of issues here on your wife's part. At the moment she has absolutely no sense of self worth! For one she's been so used to being dominated and verbally abused as a child that she's never really had to think for herself, her mother did that for her. She's went from one job to another getting by and no more and if she's been sacked then she's told herself it's because she's no good anyway, mom has always told her that. She's never HAD the chance to fend for herself, you came along and took over and looked after her. Can you see where I'm coming from?
She mopes around the house watching TV and doing the minimal of tasks. She's put on piles of weight too through lack of exercise. It's as if she's on self destruct just WAITING for you to tell her she's hopeless, no good and that you're leaving her. The truth is... she doesn't know HOW to...
Counselling would certainly be an advantage here but she's very against that (too intimidating for her) so don't force her, leave that for now. She needs to see that she IS worthy! She IS needed and that she IS a wonderful person.
What I would suggest is to take things one step at a time. Don't expect her to turn everything around in one day as this is expecting the impossible. Instead use reverse psychology. Say to her for example that the bathroom could do with a good clean and would she do it today? Ask her to be really thorough with it and you'll be doing an "inspection" when you get home. Laugh about it though and keep it light and not too serious. Kiss her when you leave for work and remind her again about the bathroom. When you come in at night go check to see if she's done it. If she has praise her to the hilt! "Wow, you've been busy today, the bathroom looks amazing." It's only one room but she's achieved something so praise her for it. It will make her feel good and she'll WANT to do something else for more praise. Sit with her at night and tell her how proud you are that she made such a good job of the bathroom. Make a lot out of it. Deep down she's just like a little child herself and she NEEDS constant praise when she does something right and like a child she'll WANT to please you again! Continue like this with other little tasks (just one thing at a time) and go overboard with the praise when she does it. This will build up her self esteem and in time she'll start to do things without you having to ask.
Make sure too that when you go shopping you buy in nutritious and healthy food. Remember, we are what we eat! Buying snacky foods will cause her to feel lethargic, she'll have no energy and feel listless all the time. If she's used to putting a lot of fatty or sugary snacks in the basket then YOU do the shopping and buy in wholesome food. She can't eat what's not there.
Remember too, even although she's only working around the house, this is still exercise for her and she'll start to feel good. She'll feel good that she's cleaned the bathroom thoroughly, she'll feel good that you NOTICED and told her and she'll start to think what else she can do to get that praise again. Take time out at night when the kids are in bed and again let her know how you were so proud of her and the work she did on the bathroom. Do the same again with another room in the house and again, lots of praise if she does it.
In time you'll find that you won't need to tell her about her appearance, she'll WANT to tidy herself up and look good, not only for you but for herself as her sense of self worth will have started to rise. She's been down on herself for so many years and the verbal abuse and control from her mother is very deeply ingrained but with your love and help this CAN be turned around. You just need to be patient and a little bit clever!