Telford joined Leeds in 2007 from relegated club Sunderland. In May of that year she had turned out for Charlton Athletic in a tournament in Spain, but Charlton disbanded their women's team shortly afterwards. At Leeds Telford was named player of the match in the 2008 FA Women's Cup final, after an impressive performance in Leeds' 4–1 defeat to Arsenal.
In summer 2010 Telford was called into the England squad as an unattached player, having left Leeds Carnegie. Matt Beard signed her for Chelsea Ladies ahead of the inaugural 2011 FA WSL season. In October 2012 it was announced that Telford would join Australian club Perth Glory for the 2012–13 winter season.
Telford left Chelsea after three years in December 2013, signing for Notts County ahead of the 2014 FA WSL season. There she was reunited with her former Leeds coach Rick Passmoor and she would have the opportunity to train with goalkeeper coach Kevin Pilkington. Chelsea coach Emma Hayes' decision to hand Telford a free transfer left her shocked and raging.
Telford was carrying a shoulder injury ahead of the 2015 FA Women's Cup Final and Notts County were angry when The Football Association refused their request for dispensation to sign another goalkeeper. Telford recovered to play in the team's 1–0 defeat by Chelsea at Wembley Stadium. She signed a two-year extension to her contract in November 2015.
In June 2016, Telford suffered torn ankle ligaments in a win over Doncaster Belles and was ruled out for three months. Notts County moved quickly to sign Lizzie Durack as a replacement.
She debuted for the senior national team in March 2007 against Scotland, having previously played at Under-17, 19, 21 and 23 levels. She was called into the 2007 FIFA Women's World Cup squad as back-up to Rachel Brown and Siobhan Chamberlain.
In May 2009, Telford was one of the first 17 female players to be given central contracts by The Football Association.
In May 2015, Mark Sampson named Telford in his final squad for the 2015 FIFA Women's World Cup, hosted in Canada. England eventually finished in third place, but Telford was disappointed to be the only member of the squad not to play any minutes at the tournament.
Telford attended Tanfield School, then Gateshead College on the Talented Athlete Scholarship Scheme.