E.G.
I'll say if she does let you know that she doesn't feel it coming it's safe to say it's time to see her doctor. This could be a sign of bladder stem troble, her bladder has troped, nerve issues, or something closly related. I'm thinking some kind of nerve disorder. Don't be alarmed until you hear what her doctor has to say.
It could be nothing more the rlapes since you have a younger child. My son of three started to do good on the potty, yet when my 2nd son come along he backed tracked, plus My husband and I had problems to where we are going through an divorce. Keep us posted we are out here for you.