C.,
Even though my daughter, also 3 never went through this, rest assured that this is somewhat normal. I think the worst thing that you could do is to put pressure on her or punish her. You have to use positive encouragement, and have lots and lots of patience!!! Don't worry about what others say and think, either. Slow and steady wins the race when it comes to toilet training. Most likely, your child is fearful of having a BM in the potty for some reason. You can help ease her anxiety just by talking with her and explaining to her that having BM is natural. Also let her know you think she's old enough now to be able to go poopoo on the potty. You can even ask her if she's scared, showing her you genuinely care for her feelings. A great tool for this is a book called Everyone Poops, by Taro Gomi. Be careful not to make her feel bad or ashamed about her refusal to have the BM on the potty. I think it's better for her to have the BM in a diaper than to get constipated because she is scared to go on the potty. Try to be patient, I know it's very hard with a 3 year old, but just remember that she won't do this forever!!! She will eventually start to go on the potty, you just need to keep with the gentle encouragement, and don't ever, ever punish her. If she has an accident, you just tell her, that's okay...you're still learning, let's get you cleaned up. Next time try to remember to tell mommy you need to poopoo on the potty. Hang in there. It won't last forever!!!! Congratulations on your twin pregnancy!!!