The Young Mares finish second in Group B behind South Africa, who maintained their 100 percent record with a 3-1 victory over Madagascar at the St. François Xavier Stadium.
Rantsho was unstoppable as she mesmerised the Seychelles defence, with a penalty and two free-kicks among her haul of goals.
She was closely followed by Pearl Sikwane, who also netted five times in what was an utterly dominant display. Kaone Mbongwe, Tlhompho Gabana and Lorato Motlogelwa (two) were also on the scoresheet.
Seychelles were able to celebrate their first goal of the competition, which will have been a great relief to them, as Kimbelly Chan-Tak-Hue what is a historic striker for the islanders for in this competition.
South Africa eased to a 3-1 win over the Malagasy despite missing talismanic captain Jessica Wade through injury.
Nelly Gamede opened the scoring midway through the first half with a long-range effort that cannoned in off the crossbar, before adding as second from the penalty spot.
Oyisa Marhasi took her tournament tally to nine when she raced onto a through-ball and slipped the ball under Madagascar goalkeeper Chrystina Faraniaina.
Madagascar barely threatened the South African goal but won a penalty with a little more than 10 minutes to go, which Marie Raveloarisoa finished with aplomb.
Thursday will be a rest day at the competition, but the action resumes on Friday with the semifinals.
Uganda roared into the knockout stages with a 20-0 win over Comoros Islands and will want to continue that form when they play Botswana at the St. François Xavier Stadium (kick-off 12h00 local time; 08h00 GMT).
The East Africans will also have the benefit of an extra day off and so may be fresher than the Young Mares as they seek to become just the second guest nation after Tanzania (2019 COSAFA Women’s Under-20 Championship) to go home with the trophy.
Uganda scored an impressive 32 goals and conceded just one in the pool stages and will be a formidable opponent for Botswana.
South Africa will face Zambia in the other semifinal (15h00; 11h00 GMT) and having been the only side to come through the pool stages with a 100 percent record, can go into the knockout rounds with some confidence.
Zambia have shown excellent form as well though with their only dropped points a 1-1 draw with Uganda in their opening match, in what has otherwise been a dominant display from the team.
Seychelles 1 (Chan-Tak-Hue 18′) Botswana 14 (Sikwane 1′, 45’, 65’, 75’, 84’, Motlogelwa 10′, 90’, Mbongwe 17′, Rantsho 20′, 28′, 37’pen, 55’, 61’, Gabana 85’)
Madagascar 1 (Raveloarisoa 79’pen) South Africa 3 (Gamede 22′, 30’pen, Marhasi 66’)
Uganda vs Botswana (KO 12h00) – St. François Xavier Stadium
South Africa vs Zambia (KO 15h00) – St. François Xavier Stadium
Group A P W D L GF GA Pts
Uganda (Q) 3 2 1 0 32 1 7
Zambia (Q) 3 2 1 0 24 1 7
Mauritius 3 1 0 2 5 20 3
Comoros 3 0 0 3 1 40 0
Group B P W D L GF GA Pts
South Africa (Q) 3 3 0 0 36 2 9
Botswana (Q) 3 2 0 1 21 6 6
Madagascar 3 1 0 2 17 9 3
Seychelles 3 0 0 3 1 58 0
Matches Played: 12
Goals scored: 137
Biggest victory: South Africa 28 Seychelles 0 (Group B, September 21)
Most goals in a game: 28 – South Africa 28 Seychelles 0 (Group B, September 21)
14 goals – Juliet Nalukenge (Uganda)
9 – Oyisa Marhasi (South Africa)
7 – Florence Kasonde (Zambia)
6 – Bofelo Rantsho (Botswana), Alinah Lalasoa (Madagascar), Tiffany Kortjie (South Africa), Margret Kunihira, Fauzia Najjemba (both Uganda)
5 – Pearl Sikwane (Botswana)
4 – Jessica Wade (South Africa), Shelly Masumo, Cindy Banda (both Zambia)
3 – Lydia Razanajohary, Marie Raveloarisoa (both Madagascar), Tiyana Carollissen, Nabeelah Galant, Sonika Mzingeli, Nelly Gamede (all South Africa), Shakira Nyinagahirwa (Uganda), Tisilile Lungu (Zambia)
2 – Yaone Modise, Christinah Monyatsi, Lorato Motlogelwa (all Botswana), Jenny Randriamialimanantsoa (Madagascar), Jerusha Ramasawmy (Mauritius), Sonika Mzingeli, Christy Noble (both South Africa), Maweta Chilenga, Comfort Selemani (both Zambia)
1 – Tlhompho Gabana, Kaone Mbongwe, Serati Modisenyane (all Botswana), Moinahedji Ali (Comoros), Iloala Aniera, Laurencia Raheriarisoa, Charline Rondromalala (Madagascar), Marie Quirin, Marie Verloppe (both Mauritius), Yolanda Ndluli, Shakira O’Malley, Hlela Philisani (all South Africa), Stella Musibika, Daphine Nyayenga, Gillian Akadinda (all Uganda), Esther Banda (Zambia)
Own goal – Soukaina. Maenfou (Comoros)