Why would a girl still be leading me on?

so we had a thing and i thought we were gonna be a couple. then out of nowhere she started giving me short responses but still seemed interested. then i found out she got back together with her boyfriend or this guy became her boyfriend. so i took it that this why she was giving me short responses. but she still kept giving me smileys and making it seem like she was interested. so why would she keep leading me on instead of just ignoring me or telling me she has a boyfriend or doesnt like me anymore. id rather her tell me straight up. she even kept sending me snapchats and stuff. Would it be best to just ignore her for playing me?