Mainland came out on top 5-3 after the sides were locked 2-2 at halftime.
Muirhead's industry and skills were mirrored by many in Steve Brook's National Women's Youth League side, which opened the scoring after nine minutes.
Holly McNight equalised for Mainland 10 minutes later.
Muirhead re-established Footballsouth's lead, but the visiting side replied on the stroke of halftime and some heads went down at the break.
Footballsouth goalkeeper Tess Nichol pulled off some fine saves in the second half, but Mainland started to dominate, despite an inspiring match in midfield by Kushla Glover.
Gabrielle Brodie and Zara Walker scored, and under increasing pressure at set plays, Footballsouth conceded an own goal.
The irrepressible Muirhead scored again in the 90th minute, but by then Footballsouth was a shadow of the energetic side in the first half.
Mainland coach Mike Sharkey De Bono was pleased with his team's recovery and conceded Footballsouth had the edge in the first spell.
Footballsouth's youngsters, such as Shontelle Smith and Jordyn Walker, impressed around the experience of Muirhead, Glover, Georgie Brown and frontrunner Mary Fraser.
But until match fitness and stamina are achieved by the squad, which comes from a wide area - Queenstown, Invercargill, Temuka and Timaru - progress will be difficult.
