Prompt: shoot (or: at least she has Garrus and twenty-odd factors of 'win' on her side; 1 of 5 ways Shepard and Co. could have gotten Santiago for Massani)
Follows: ashamed
The bug is an expensive bit of tech Specter Requisition doesn't know about. The R&D guys from somewhere managed to run afoul of the Shadow Broker, or maybe just Liara. Shepard kept the prototype to appease her friend, for the times in deep space.
It's been surprisingly useful.
She says 'goodbye' and tosses it to Garrus, who drops it into rifle barrel with a skill called Luck. They don't know how it works, and despite the theoretical, she doesn't even know if it'll hold on impact.
With Garrus, the shot is not impossible and it slips though Santiago's rear guard.