Okay, bit of a problem with the category here. WB/DC characters parodying Marvel characters with a nod to an old TV series which had nothing to do with either of them.
The girl on the right is Marcie Fleech, a recurring character in the two seasons of Scooby Doo: Mystery Incorporated. She started out as a villain and science fair rival to Velma but by the end of season two they were close friends. (Cue wild speculation in the fan community about how close.)