The Mounties defeated Gadsden City 59-54, using high-energy defense in the second half to take control.
Shades Valley forced only seven turnovers in the opening half, and the Mounties trailed 31-26 going into intermission.
"At halftime, we made some adjustments," Shades Valley coach Tonya Hunter said. "We played a little harder in the second half."
As a result, Shades Valley forced 19 more turnovers, took the lead for good with 4:38 to play and won its way into Friday's finals. The Mounties will face Huntsville at 9 a.m.
Frantisha Tyson led Shades Valley (31-1) with 17 points, while Morgan Williams added 15 points, five assists and six rebounds. She had a key three-point play with 57 seconds left, pushing a one-point advantage to four.
For Gadsden City (22-9), Takara Blount had 13 points, while Dajia Williams had 12 points and 11 rebounds.
Sports Editor Mark Edwards: 256-235-3575. On Twitter @MarkSportsStar.