I'm sorry, but I disagree with a lot of you. I think signs do exist... Telling you that they have done a wee/poo, stopping what they are doing to do a wee/poo are a couple of examples. I think this means they are ready. I think that the poster's child probably is showing these signs (due to her saying that she does a wee on the toilet/potty) but have probably been ignored. However, I don't think it's fair to call it lazy. She probably wasn't aware. It would be lazy to now put it off, for school to deal with, as she now knows. However, I don't think it's fair to just call her lazy now.
I think it's important to wait for these type of signs, but with showing them the toilet (I preferred to skip the potty) and letting them sit on it while you're in the bath, etc. I know it sounds gross, but also letting them see how you use the toilet, so they understand. My two children were toilet trained by the time they went to nursery, with very few accidents. I don't think it's fair to shame them into toilet training.
We used a chart, you got a sticker for weeing, 2 for pooing. If you had a wee accident, 1 gets taken away, if you have a poo accident, 2 get taken away. This is because the 'underwear fairy' needed you to get a certain amount of stickers before you were ready for underwear. We never used underwear until they got a certain amount of stickers, they just went around the house naked on the bottom half. It worked really well, as they knew that stickers were being removed due to them being further away from their pants, not because they were naughty.
When they reached the 'underwear fairy', the fairy left them a whole set of underwear. The smile that it brought them was priceless! They were so excited. Then we set up a new chart, with the next intensive being a toy, so the 'underwear fairy' brought them a toy if they got enough stickers, due to them looking after the underwear (not ruining them).
I couldn't recommend this strategy enough 