Deja Rawls scored 10 of her 14 points in Abington's 14-2 second quarter, and the Ghosts clinched a berth in the PIAA state tournament for the first time since 2010.
Rawls added three assists and three steals. Senior Michael Harris scored nine points and grabbed 12 rebounds.
Haley Warden led Garnet Valley with 10 points and 10 rebounds.
"I really think that they thought they could not lose," Marsh said.
Also in the second round:
Grace Phillips scored five points in the fourth quarter and No. 8 Bishop Shanahan topped visiting, ninth-seeded Ridley, 38-31.
Nicole Munger scored 20 points with three steals and Corrine Godshall paired 14 points with nine rebounds to propel No. 5 Central Bucks West past visiting No. 12 Methacton.
Carly Monzo and Colleen Steinmetz each grabbed six rebounds and Mount St. Joseph, the top seed, cruised past visiting, No. 17 Souderton, 52-36.
Bri Cullen hit two late free throws to seal third-seeded North Penn's 43-40 win over visiting Central Bucks South, the 14th seed.
Karoline White's seven points led No. 22 Central Bucks East at No. 6 Upper Dublin, 18-15.
Shelby Mueller scored 21 points, grabbed 14 rebounds, and added three steals to lead No. 4 Spring-Ford past visiting Penn Wood, the 13th seed, 55-49.
Tim Guers scored 10 of his 27 points in the fourth quarter to lead Germantown Academy's rally, but it was not enough as the host Patriots fell to Kiski Prep, 75-73, in the quarterfinals of the state Independent Schools tournament.
District 1. Andrew Chobany scored 21 points, and No. 7 West Chester Rustin eased past visiting, 30th-seeded Wissahickon, 73-41, in the Class AAAA second round.
Delco Christian heavyweight Scott Pendell captured a first-period pin and shared outstanding-wrestler honors and his father, Greg Pendell, shared coach-of-the-year honors at the Bicentennial League championship meet at New Hope-Solebury.
Greg Pendell received a diagnosis of pancreatic cancer early this season and is recovering.
Lower Moreland's Dan Park also was named coach of the year, and the Lions won the team title. Rich Cerebe of Calvary Christian won at 152 pounds on a first-period pin and was named co-outstanding wrestler.