My middle child (who is turning 4 in 2 months) was difficult to train (and still isn't poop trained). She was physically ready to be trained around 18 months of age had all the readiness signs but just mentally wasn't there yet. I tried nearly everything for 2 years off and on (we would try occasionally see it wasn't working then decide to try again later). We finally got her peeing on the potty in February. What was the change? When she was around 3.5 she finally started caring that other kids her age that she liked hanging around with weren't wearing diapers. This coupled with the fact that she realized she wasn't going to be able to go down the big water slide on our vacation because you can't have swim diapers in the pool.

My advice would be to wait a few more months, when she is closer to 3.5 (if this isn't before the school deadline). There is a mental shift that goes on around 3.5, we saw it with my daughter and potty training and her shyness. She started to get interested in other people and wanting to play with friends. Tell her now something like "we'd like you to start going on the potty because there are cool things we'd like you to do that only big girls who don't wear diapers get to do." Then just wait for her cues to when she may want to start trying again. Also during this time make her an active participant in changing her diapers. She has to wipe, she has to throw the diapers out.

If you don't decide to wait please don't punish her for accidents. This can backfire. You may have a situation where she starts not peeing at all. We never punished my daughter for accidents, but I know she picked it up that we were frustrated when she peed all over the floor one time when we were trying. Our words said we didn't care, but our body language said otherwise. After that she began not peeing at all and would get in phases where she would hold her pee for a ridiculous amount of time (she went over 24 hours at least two times in a span of 3 months).