Why did she do this? I'll answer yours?

[Jack]

I met a girl on the bus and she gave me her number when I asked if she was single, she said she was single. So we been texting etc she texts me as well as I text her. She asked where I worked then a few days later she comes in for a meal with her boyfriend at the restaurant I work... Why is she messing with my head she told me she was single then bam this why would anyone do that? Playing with my emotions or making me jelous?
I don't understand why she would deliberately try hurt me when I was always nice.
It's definitely her boyfriend as my friend checked on facebook when I told him. She was with her boyfriend so she blanked me like she didn't know me.