SUBREDDIT: r/relationships
TITLE: I [23 M] need to find out if this girl [21 F] is actually interested in me or if she's just jerking me around
POST: We were talking for a while last summer, but she ended up in a relationship with a dude she was involved with before I met her, so I figured that was that.

But, for the past month or a little before Christmas anyway she's been all over everything I post on Facebook. She's also been posting all this forlorn shit that occasionally is obviously referring to unhappiness she feels in her relationship.

Honestly, I don't really want any attention from her if she is not actually romantically interested in me. I feel like she should understand this already but I guess not. How can I talk to her about this in a way that sets the record straight but where I don't, yknow, come across as an asshole?
TL;DR: 
need to talk to this girl who has a boyfriend to find out if she's actually in to me or if she just wants attention, without seeming like a dick about it