My daughter is exactly the same except she's nearly three. I just give her a nappy anytime she needs a poo throughout the day. I figure she's got till she's 18 to get it right. How many 18 years old wear a nappy when they poo?! I'm not worried about my daughter and neither should you be. Relax!
She'll probably get it when she goes to school/nursery. You may cause more problems by trying to force her to poo in the loo before she's ready. (constipation?)
Try backing off a bit and let her poo where she feels comfortable for a few months, then suggest the loo again, but don't force it.