So... catfight? (pass Joker the popcorn already)
Though, while Liara probably should be using her biotics offensively instead of just for Warp Ammo, she at least picked the right weapon due to Tali's reliance on shields. An SMG is best suited for battering down shields with rapid fire, and the Shuriken is one such gun.
That said, if Tali's smart she picked up Damping again from ME1 to shut down Liara's biotics, which would dramatically turn the tide in Tali's favor as shotgun skills is something Tali is definitely ahead with as a method of making Liara Embrace the Goddess...
Either way, it'll be an impressive fight for all the people watching in the Armax Arsenal Arena viewscreens