Victoria Waterfield was a young Victorian woman who was used by the Daleks to force her father into luring the Doctor into their trap, trap which he and Jamie inevitably spring. Eventually, the Daleks' evil machinations, lead to Victoria's father sacrificing himself to save the Doctor's life. His last wish is for the Doctor to take care of Victoria. The Doctor does so by letting her join the crew of the TARDIS.
Although Victoria on the surface appears to be a proper Victorian lady, she shows she also has plenty of resolve and determination when necessary. Of course, she does tend to do a lot of screaming when confronted with bizarre creatures like the Cybermen and the Yeti, but what would you expect when faced with such sights. Perhaps, that is why Jamie becomes very fond and protective of Victoria. He is truly heartbroken when Victoria chooses to leave the TARDIS at the end of Fury From the Deep.
Despite enjoying the company of the Doctor and Jamie, Victoria decides that she is not cut out for existence aboard the TARDIS. The last we see of her, she is settling in with the Harris family in the 20th century.