2 years old is a good time to start. Personally, we started pre-potty training at 7 months old, so it was a slow and steady journey, which we enjoyed.
Feel free to read what we did at 18 Sure-Fire Tips for Early Potty Training Success | Mummy's Reviews
My boy doesn't poo at fixed time too. I started by recognizing his expression when he's about to poo. Then quickly brought him to potty to poo. And taught him to tell (or use hand sign) to indicate his poo urge. At 15 months old, he finally succeeded.
Pee took longer to day-train as he needed to gain enough bladder control to hold pee until reaching the potty. Instead of asking too frequently (I dont't want to sound naggy), I observed his diaper wet patterns. (I put on non-waterproof cloth diapers on him for a while and noted he pee-ed about every 1+ hour.) So I brought him to pee at the potty every 1-2 hours. Just before 2 years old, finally day-trained.
Personally, I continued letting my boy wear cloth diapers or training pants during training. Let him switch to underwear only when almost fully succeeded. Reason is I want to prevent frequent wet floor (in case he slips) and protect his books, toys, etc. Less heavy laundry / cleaning to do. Also, our gradual training went on for many months, like running a marathon.
Do what's most comfortable for you and your girl. Different folks, different strokes. And dont't expect quick result cos your girl may feel the stress and resist the training. Happy potty training!