Mom found his ambiguous information from dad's mobile phone, and later she forgave him, but since then, mom has liked to look through his mobile phone.

Maybe it's not an ambiguous message at all. Your father has nothing to do outside. It's because your mother loves your father too much and is afraid that your father will leave, so she is very nervous. But it may be a bit ambiguous, but this is just a guess, and there is no evidence to support it. Even if there is, maybe your father is just playing, and his heart is still filled with your mother and daughter. Men are really playboy, but men are more emotional than women. It's very bad for your mother to always read your father's cell phone messages, which affects her feelings and has no effect. Please advise her.