Beetee compares Wiress to a canary in a coal mine, and that's exactly what she is for the other tributes in the arena. Her death is cruel and sudden, but it also serves as a warning to her allies that their enemies have appeared, giving them time to prepare a counter-attack.
Wiress, a District 3 victor, seems to be a nice person who doesn't deserve to go back into the competition a second time. Wiress is also loyal and devoted. She understands the importance of their cause, and even in death she's holding on, steadfastly, to the weapon Beetee so desperately needs. We don't learn much about her other than that she's a good inventor who's extremely observant, smart, and unable to withstand the horrors of the arena during the Quarter Quell.
Despite being horribly traumatized by being thrown into the arena a second time, Wiress is the first tribute to figure out the arena's design. She knows it's a clock, and with her incessant repetition of "tick tock," she manages to get this idea across to Katniss.