It's not easy to stop or break kids' bad habit

Look a my daughter's photo below. What can you imaging she was doing? Playing hide and seek? Sad and crying? Trying to get our attention? NO! She was actually pooing :( Funny isn't it? She developed the habit to stand and poo. Sometimes she even need to find her "usual" spot before she can poo. Whenever she feel like pooing, she will ask us to wear her the diapers, as she can't do it with her pant. We tried to break this bad habit of her but doesn't seems to success after few months. We tried whatever we can to let her sit on the potty by bribe her with the things she likes. That only can make her sit on the potty for a while but she wont focus on doing her big business. If we keep forcing her, she can keep her stool 2 days without letting it out and started to complain about stomachace. So we have to give in finally. Can't seems to do much now except keep telling her that other kids are pooing in the potty and show her those pictures....It's really not easy to stop or break the bad habits of kids, what's more adults, right? :(