I have also been toilet training my daughter and at first she also was fine with wee but worried about poo. I had to just let her have accidents as she would get upset if i tried to get her to sit on the potty for a poo, i always stopped trying if she was upset, so she had a lot of poos on the floor and in her knickers but every time i said never mind and put the poo in the potty and said yeah thats where poo goes, i did also show her mine in the toilet! then one day she just did it on the potty and was fine, i think maybe you should do this until she isnt worried and just be very relaxed and patient with her, give her lots of water to drink and plenty of fibre and fruit and veg, then she wont get constipated or be able to hold it.