Gerri first appears when Wanda is watching TV, when she shows a (fake) photo of the Monster of Walker Lake, surfaced at the crack of dawn. Wanda is intrigued and calls upon the rest of Ms. Frizzle's class to check it out.
Gerri then appears again flying in her helicopter, warning the kids to stay out of the water and that it's too dangerous to go swimming in the lake with the Monster out there. Nevertheless, Wanda ignores her warning, stating that Gerri doesn't own Walker Lake and they could search for the Monster if they wanted to.
Later on, after Ms. Frizzle and the class attach sand filled barrels to The Bus to help it dive, Gerri shows up in her submersible. After she notices them, she says that it looks she's got "some competition". She drives up to the bus with the Frizz and the kids not noticing and activates her submersible's claws and unties the ropes holding the barrels onto the bus, causing them to break off and allow the Bus, the Frizz and the kids inside to float rapidly up to the surface.
"No one's going to ruin my story, especially a bunch of lousy kids!" - Gerri Poveri
Later on, after Ms. Frizzle and the class try crumpling up the bus to a small size to reduce its bouyancy, Gerri notices them again and angrily asks herself if the Frizz and her students ever give up. Later, when Wanda became entangled in a cluster of seaweed while looking for the Lake Monster, Gerri notices her and declaims she's sunk if Wanda found her Lake Monster. After Wanda does find the Lake Monster and realizes it's not real but an inflatable balloon animal, Gerri shows up in her submersible and explains she was faking the Monster in Walker Lake story to boost her ratings, and sabotaged the Bus' barrel weights from earlier to prevent them from uncovering her ruse. Wanda gets furious with her and exclaims she won't get away with it. But Gerri meanly tells her that no one will believe her; she's just a kid.
"We'll see about that!" - Wanda
After Ms. Frizzle and the class use air pumps to pump the water out of the bus' pontoons, Gerri sees them floating back up to the surface in order to stop her from faking the Monster of Walker story. She then evilly tells Wanda to sink again and activates her submersible's claws again and drives up to the rising bus and then pops out the corks, flooding the pontoons and causing the class to sink again. Expecting she has succeeded to drown the kids, she evilly leaves them as the bus crashed back onto the bottom of the lake. Back at the surface, she pushes a button on her remote control causing her fake Lake Monster to rise upwards towards the surface. She plans to lie to her audience, making everyone think she found the Monster. She turns on her camera and starts her next story about the Monster of Walker Lake.
While she was doing her next story making everyone in Walkerville think there's a Monster in Walker Lake, Ms. Frizzle and the class come up with another plan to help float them back to the surface. After the kids and Ms. Frizzle uncrumple the bus so that it gains buoyancy, Wanda and Tim cut the cable holding the fake Monster, causing it to float up to the surface. As Gerri kept on doing her next Monster story, the Monster suddenly pops up right underneath Gerri's helicopter causing it to capsize and Geri to fall into the water as the bus pops up from the surface. Gerri starts crying and complaining that her story is ruined and Wanda exclaims that it's really she and her friends' story. Wanda pulls the cork plug out of the Monster, causing it to deflate and fly all over the place and land flat on the surface.
Back at the In Your Face studio, Gerri knew she now had to apologize to her audience. She does so, and everyone accepts it. Wanda then explains to Gerri how she and Tim got her fake Lake Monster to float up to the surface. She cut the cable, caused the Monster to float upwards, and then her very own Monster ended up "In [Her] Face!".