Felt like researching it...here are some players who graduated the same class and scored a combined 4000+ with their teammate. I'm sure there are several more I didn't find:
Cynthia Cooper and Cheryl Miller are close with 4577...they'd likely be much higher if they played 38-39 game seasons like they do now.
McGee twins combined for 4560 at USC, same thought process as above.
Kelsey Mitchell and Alexa Hart combined for 4537 at Ohio State.
Stiles and Mitchem combined for 4532...Mitchem was only there for 3 years though, so they'd likely be above Plum/Osahor if she played 4 years.
Beth Morgan/Katrina Gaither had 4448 at Notre Dame.
Shenise Johnson and Riqina Williams hit 4410 at Miami.
Beard and Tillis had 4399 at Duke.
Brittney Griner and Kimitria Hayden hit 4388 at Baylor
Miller twins had 4307 at Georgia. Played 3 years with Deanna Nolan too there.
Coleman/Toliver had 4283 combined at Maryland
Mavunga and Mitchell possibly would've topped the list if Mavunga played 4 years at Ohio state. Even in just 1.5 years of Mavunga, they combined for 4235 points. If you count Mavunga's years at UNC, they scored 5135 combined. They also they were different HS classes but finished at OSU at the same time.
Stewart and Jefferson had 4208 combined.
Catchings and Randall had 4128. They'd be a lot higher if Catchings didn't have her ACL.
Tashia Phillips and Amber Harris combined for 4100, they were different HS classes but same graduating year.
Little and Latta hit 4058 at UNC
Kelly Mazzante/Jess Brungo combined for 4061 at Penn State.
Paris twins had 4002 at OU.
On their way to joining this list besides Collier/Samuelson is this board's favorite duo of Marina Mabrey/Arike Ogunbowale. They're at 3471 right now. If you count Turner/Ogunbowale the same class, they're at 3535.
Some noteable duos who came close were:
Breanna Stewart/Morgan Tuck at 3974
Morgan William/Victoria Vivians at 3927
Chamique Holdsclaw/Kellie Jollie at 3919