Dominance And Submission

I have a question from a fellow Dom he is considering making a lady his sub ,she has said that she is considering several Doms and has not submitted to any of them or a choice yet.
They talked along time yesterday and she became disrespectful to him he told her she would be punished for that she agreed to a punishment, he offered a sexual punishment and play telling her she will not stop till she has an orgasm , she said she couldn't do that because another Dom had punished her by making her insert a plug for to hrs and forbid her to play or have an orgasm . now he is wondering by submitting to the other Dom and having sex play with him does that mean she made a choice and chose the other Dom already as her new Dom .