We started potty training my daughter at 18 months - she is 2 years 3 months now...
Not only was her little sister on the way, but we aslo have a super-competitive friend that was trying to beat us to potty training - so we just knew we had to potty train her and do it FAST. There was no way I was going to have TWO in diapers OR let my friend potty train her daughter before mine. HA!!
But what you're doing sounds exactly what I did... sat her on the potty throughout the day, tried leaving her naked (just ended up with puddles all throughout my house), tried going straight to the big girl panties, sticker charts, M&Ms, portable potty seats, seats that attach to the big toilet, etc. You name it, we have tried it.
We gave up after a few months because although we had some successes, she had no interest at all (and still doesn't). Occasionally, we will see the "signs" of an oncoming bowel movement and will make it to the potty in time. But for the most past, we are wearing pull-ups (because they are easier than diapers at this stage) and that's about it. We are no longer forcing the issue and assume she will gain more interest in time.
Of course, we celebrate our successes and hope that she will eventually make the connection - she will... in time.
We had to give up on being the first mom to potty train as well (and I guess I do find comfort in knowing her daughter is still NOT potty trained either - ha!!)
Just don't rush or stress or fret. She is her own unique little person and it will happen when she chooses - on her own time. GOOD LUCK!!! :)