Take a 10 foot piece of 4" PVC pipe, glue an end cap on one end and a female adapter on the other. Put a piece of electrical tape in the middle so she knows where to try to center it. Put a gallon of water in it just to test it and then screw the plug into the open end. Have her pick it up and hold it on her shoulders the way she would hold a barbell if she was doing a back squat. Tell her to walk. If a gallon is too much take some out, if it's not enough add some. Don't fill it all the way up, that will defeat the purpose. You want it to roll and you want her to have to balance it with every move she makes. Have her do some lunges, have her do some squats, it's brutal and sssssooooo much cheaper than a trainer. Costs maybe $30.00 total and it lasts forever.
Go easy at first, she will find core muscles she didn't know she had.