Why didnt she tell me she is in a relationship?

me and this chick used to date. She broke it of, long story short, outta the blue one nite I texed her drunk I ythink asking for n*des of her. She talked to me normal, sayin she got my text and almost sounded like she was interetsed even putting a smiling face!. Come to find out she has a bf. Is this strange..?