Just started PT with my DD (2 yrs 3 mths) and seems to us that the accidents are the way they will learn. If you put proper pants on them, they will feel that they are wet, and then you can explain the concept of feeling the need, asking to go, etc.
Over the weekend, we let our DD wonder around in minimal clothing, and kept the potty near by, and by the end of the weekend, she was deciding herself to go and sit on the potty when she needed to. But, she is in nursery now for a few days, where she will need to ask to go and need help with her clothes, etc, which is a lot more difficult, but again, I think the accidents will help her to learn to think further ahead and ask before it is too late. Not sure if you are using pull-ups or anything, but I am avoiding them because I think they will confuse - there is no need to ask to use the potty if they can just go in their pull-ups and suffer no consequences - it is just like being back in a nappy.
Trial and error I think.
But, just a thought, if your DD is just about to start nursery, might it be better to wait for her to settle in before PT? It might be too much all at once? Just a thought.
Try not to feel bad about letting her go to nursery - it is hard I know, but she will get so much benefit from it, mixing with lots of other children and doing loads of activities that you can't do at home. You will probably notice her development speed up once she is settled in because she will copy all the older ones. I think nursery is really good for them. But I know it is hard