Gallacher made her senior debut aged 14 playing for
Forfar Farmington. and won five trophies: two
Scottish Women's Cups and three
SWPL Cups. In July 2022, Gallacher signed for
Celtic. She won the Scottish Women's Cup in her first season with the
Hoops, also scoring 16 league goals as the team narrowly missed out on becoming
Scottish Women's Premier League champions for what would have been the first time in their history. She was nominated for the
SWPL Player of the Year (it was won by teammate
Caitlin Hayes). A year later, Gallacher's 90th-minute winning goal against former club Hibs clinched the
2023–24 SWPL title for Celtic on goal difference. Gallacher represented Scotland at youth levels up to the
under-19 team. She made her full international debut for
Scotland on 22 September 2023, appearing as a substitute in a
Nations League match against
England. ==Playing style==