Mk17 SCAR. Can't tell which variant of it, though. I'm guessing it has a longer barrel due to the way she's canting the rifle sideways to maintain cheekweld, but allowing her access to her miniature optic for close encounters.
Optic: Elcan SpecterDR/Docter Reflex Sight (Yes, Docter with an e.) LAM/IR Illuminator: Insight AN/PEQ-15 Foregrip: Tango Down VFG
No curve in the mag, would lead me to believe a SCAR Heavy.