Stranger proposed in train Banglore

When my friend was travelling in a train, suddenly, a stranger comes near him and started flirting with him. She said he was looking very handsome and she wants his number, so they exchange number and in a week or so, she suddenly put up that she wants to marry him and they don’t even know each other fully yet, he said no for it but still continued to talk and later, she implied to wanting to go out with him, and she said she was fine to even have physical relationship with him

I feel it is very strange for a unknown girl to come and reach a guy that too in a train and suddenly bring the topic of marriage that too within few days of knowing each other, and later, when he said no for marriage, she even started talking of the physical relationship makes me think that this might be a scam or a trap to extract money…