First off you aren't doing anything wrong. She is LEARNING how her body works--- it just isn't completely connected yet.
I think the first step for a child in learning to use the potty is deciding they don't like the feel of being in wet/dirty diapers - and having the skill to remove them or let you know that they need to come off.
I think some kids stay at this point for awhile --w/out developing an awareness of when they are ABOUT to go. (as opposed to "I went") Once they start to recognize the signs--- the internal impulse that says "I need to go" then the process goes more quickly. THere may still be accidents- but with my kids I found it started with "Oops I am going...." in the living room.....then the next time it would be in the hallway on the way to the bathroom..Then it is 'near the' potty....then it is 'as I am pulling my pants down'.......
I think the process is easier if they don't have a lot of cumbersome clothing to take off (less time for the muscles to release before they get on the potty)That is why summer time training seemed easier...the kids wear less and can run about the house in a long tee-shirt or dress with nothing underneath....
Keeping a potty near where they are at will also increase the chance of them making it.....
Until they make the connection between the internal signals that they have to go and getting there----the work of not using diapers falls to the parents. (YOu are being trained to watch for signs of pending potty activity or constantly taking them to the potty --in the hope that something will occur and they will make the connection. These can work - and you may find you are comfortable doing that)
My oldest was using the potty consistently at age 2 -- but my younger two were around 2 1/2. I can't really account for why there was the difference for sure.I do know that training pants and pull-ups didn't help us...Going straight to big kid pants worked best for my kids - I think they were 'cool' to them and easier to put on/take off.
Keep in mine that it is a process and will take some time.
And remember, although it is frustrating to deal with the mess.......it really isn't important how old your kiddo is when she uses the potty. Harvard doesn't ask "How old were you when you were potty trained" on their applications!