Would it be traumatic to lu train a child of 2 years of age?

Due to severe nappy rashes, my mum advised me to lu train my eldest daughter at the age of two. After six months of training, my daughter manages to urinate in her lu, but quite scared to defecate on the other hand. She is now 3 years and 6 months old but my problem is still the same. It's somehow frustrating to train her over and over again.