Before this text exchange took place, the woman apparently showed the man of her dreams something that could’ve ruined his relationship with his current GF. Her friend, the OP, told her that she shouldn’t have done that, which is pretty sound advice, but she went ahead and did it anyway.
Why? Because she was secretly wishing—no, expecting—him to drop his girlfriend like a sack of potatoes and get with her. That sounds exactly like something a “nice guy” would do to a girl who’s in a relationship. So, congratulations, young lady, you’ve become the perfect example of a “nice girl.”