Watson was named in a match squad in the UEFA Women's Champions League for the first time on 18 August 2022 as an unused substitute in the first round semi-final against Ferencváros. She made her debut in the first round final against PAOK three days later where she came on as a 73rd-minute substitute. In the second round first leg against Benfica she made another appearance, coming on in the 70th minute. In the second leg, she again came off the bench after 57 minutes and scored with three minutes of normal time remaining to take the game to extra time. The Portuguese champions scored twice in extra time to progress to the group stages of the tournament.[10][11] In December 2022 she was introduced as a substitute in Rangers' win over Hibernian in the SWPL Cup final.[12] The 2022–23 season concluded with Watson being named as PFA Scotland Women's Young Player of the Year. Rangers relinquished their league title with a home defeat to Glasgow City on the final matchday[13] and also lost to rivals Celtic in the 2023 Scottish Cup Final. It was the first Old Firm women's final and also the first final to be played at Hampden Park.[14] Watson left Rangers as a free agent in June 2023 upon the expiration of her contract.[15]
Watson has represented Scotland at under-15, under-16, and under-17 levels.[18] She was called up to the Scotland senior team for the first time for a friendly double header against Australia and Costa Rica in April 2023.[19] She made her senior international debut on 7 April 2023 starting in a 1–0 win against Australia at Plough Lane, Wimbledon.[20][21] Four days later, she scored two goals in a 4–0 win against Costa Rica at Hampden Park.[22][23] She scored a third international goal as well as making two assists in her next two caps, friendlies at home to Northern Ireland and away to Finland in July 2023 (while unattached at club level).[24]
^"2021/22 MG ALBA SWF Annual Awards". scotwomensfootball.com. Scottisah Woman’s Football. 7 April 2022. Retrieved 4 October 2022. Youth Player of the Year: Mia Scott of Glasgow City, Abbie Fearns of Celtic, Mia McAulay of Rangers, Emma Watson of Rangers
^"gers youngsters sign professional contracts". rangers.co.uk. rangers football club. 9 August 2022. Retrieved 4 October 2022. Rangers Football Club are today delighted to confirm that Emma Watson, Jodi McLeary and Kirsty Maclean have all signed professional contracts with the club.
^"'Historic milestone' for Ibrox graduates". BBC Sport. 9 August 2022. Retrieved 3 October 2022. A historic milestone" is how Rangers have described three teenagers becoming the first graduates from their girls' academy to be handed professional contracts.
^"report Benfica 2–1 (5–3) Rangers". rangers.co.uk. rangers football club. 28 September 2022. Retrieved 4 October 2022. Rangers uefa Women's Champions League journey came to an end this evening with a 2–1 defeat to Benfica in Portugal after extra time.