Born in Oxford on 30 April, 1996, Lambourne played for England at Under-19s and Under-20s level ahead of turning out for Oxford United in the second tier.
Joining Leicester in August 2018, as the team were promoted into the second tier, Lambourne's performances earned her a reputation as an effective shot stopper with strong distribution, making 29 league appearances for City across 2018/19 and 2019/20.
Although injured for much of the 2020/21 season, she did feature in the rearranged 2019/20 Vitality Women's FA Cup Quarter-Final against Manchester City, putting in a fine performance in the narrow 2-1 loss.
Lambourne also made her first FA Women's Championship appearance of the 2020/21 season as a substitute during the 4-0 victory over Charlton Athletic at King Power Stadium on the final day of the campaign.
Alongside fellow goalkeeper Kirstie Levell, Lambourne signed a contract extension in July 2021 to stay at the Club heading into the 2021/22 Barclays FA Women's Super League campaign.
Following a long-term injury to Levell, City's No.1 stepped into the starting XI, making her WSL debut against Everton on 21 November, 2021. Although it came in defeat, she was widely praised for several impressive saves.
Lambourne then kept out two penalties in a shootout with Manchester United to earn a spot-kicks success in the Continental Tyres League Cup group stage on 5 December, 2021.
She soon helped the Foxes to back-to-back wins and clean sheets at King Power Stadium either side of Christmas 2021 to move up the Barclays FA Women's Super League table, securing their top-flight status for a second season.
Featuring in 20 matches across all competitions, including four clean sheets in 14 WSL fixtures, Lambourne received the 2021/22 Players' Player of the Season prize at the Club's End of Season Awards evening.
She has now made more appearances than any other current LCFC Women squad member, playing 57 times ahead of the 2022/23 campaign, including 42 league games.