Emma

Emma was a companion of an individual calling himself the Ninth Doctor, as well as all his known successors.

Unlike past companions, the Doctor fell in love with Emma and proposed marriage to her, indicating his intent to finally settle down. However, after a subsequent series of rapid-fire regenerations culminating in a final, female incarnation, Emma broke off the engagement, saying the Doctor was, in every sense of the phrase, no longer the man she fell in love with.

Biography from the TARDIS Data Core article, licensed under CC-BY-SA