A.Y.
I know it's probably not what you want to hear, but she may just not be ready yet. The process of having a bowel movement is much more complicated with regards to muscle control than urinating. She may not have the proper control just yet. My son definitely took longer to understand his body well enough to have a bowel movement on the potty. I know you said pull-ups aren't an option, but it sounds to me like you might want to reconsider. The last thing you want is for her to feel stressed or embarassed about her accidents. I suspect it's still out of her control at this point. I'd also highly suggest picking up the book "Everybody Poops." It really helped my son take an interest in learning about this body to go on the toilet. Suddently "poop" became a fun topic and not something scary that he couldn't understand.
Best of luck to you as I know the process can be challenging. Each child really does have their own timeframe in which they are ready though, so just be patient.