Eve is good in PRACTICED hands. New players really shouldn't be using her, as you have to have a firm grasp on gameplay basics (and probably intermediates as well).
Ideas such as MIAs, jungle paths, creep timers, gank teamwork, ward placement, team-fight timing (especially since she is extremely squishy, and shouldn't engage until the fight is halfway over) are all important to understand. Eve is a kind of "win more" type character. If your team can coordinate and initiate correctly, and you can play Eve effectively, you will have no problem wiping out their team. However, if your team is losing, Eve is not a good character to help turn it around.