Chief Brossmer is the Enterprise-D transporter operator on duty when Geordi La Forge and Ro Laren are apparently lost while beaming back from a damaged Romulan ship in The Next Phase.
Brossmer appears in the fifth-season episode The Next Phase. She is at the transporter controls as the away team returns from a crippled Romulan science vessel, and struggles to hold the patterns of La Forge and Ro as interference builds. Two of the signals fade, and she has to report that they are gone.
The pair are not dead but out of phase, invisible and able to walk through bulkheads, the result of a Romulan experiment with a phased cloak.
Brossmer goes on working with Data as he investigates the odd chroniton fields appearing around the ship, readings that are in fact the trail left by his missing friends and that eventually lead to their recovery at their own memorial gathering.