Are Hailee Steinfeld and Niall Horan Dating?!

Hailee Steinfeld and Niall Horan were spotted getting flirty at the Backstreet Boys concert on Saturday night. We don't blame them! How can you not feel romantic when you hear, "As Long As You Love Me"? A source tells E! News that the duo were also seen partying to Diplo's set at XS Nightclub later in the evening! One Twitter user actually posted a video of the…