Vienna Salvatori

Vienna Salvatori was a bounty hunter who was once tasked with capturing the Seventh Doctor and Kylo Sorsha by the Wrath Justice League. She met the Doctor a couple of time, the first time she met him was the second time he met her, and she wanted to know how he knew the future. She disabled Kylo's security monitors to allow the Wrath to find him. (AUDIO: The Shadow Heart)

Behind the scenes
A series for this character was announced before her first story had even been released. However, the Big Finish team were very quick to clarify that they "do not see it as a Doctor Who spin-off. It's its own thing.  It's not set in the Doctor Who world at all."