Diapers and Silly Girls

When McKayla turned 2 I was determined that she was going to potty train. After making her hate the potty and everything about it, I gave up. Then, magically about 6 months later, she asked to use the potty. She did fine from then on. She had accidents, but for the most part did great. Now I have a new problem with my next little girl. She doesn't want to wear a diaper, she wants to wear panties. She will put on swim diapers in hopes that they are panties. Not such a great idea. As soon as her diaper is wet or messy, she wants it off. If she does not feel like involving me in the process, she will try to do it herself. So, I brought out the potty. She will sit on it, but is not really interested in using it. So, how do I keep diapers on a kid that doesn't want to wear them and doesn't really want to use the potty? I have considered duct tape, but that might be hard. I did buy some training pants, but they don't come in her size. The makers of training pants usually believe that a child that is ready to potty train should have some weight to them. My little girl is about 22 months old and still only weighs 18.25 pounds. She is still wearing 12 month clothes. They are getting too short for her, so her footie pajamas, overalls, and dresses are too short, but nothing will stay up around her tiny waist. Poor little girl, she can't wear training diapers, her cloths are too short, and she just wants to be big.