Liza Whitlock was Izzy's best friend in elementary school. From 3rd grade through 8th, those two were thick as thieves. Liza was a bit of a troublemaker but Izzy was always good at getting them out of trouble. People just naturally trusted Izzy. So she was able to get away with almost anything.
There was that time when Liza and Izzy stole every stapler and computer mouse they could get their hands on. Not to keep them. It was only to see if they could do it. Liza got caught with them and Izzy spun a tale about a local charity drive that was donating a dollar for each class accessory that's turned in. Izzy probably would've been caught on that one. But she had Abigail help her work on an official looking website.
Outside of that, Liza was simply a very good friend to Izzy. When they first met on Liza's first day at school, Liza was the only kid who didn't make a big deal about Izzy being a cyborg. Liza also encouraged Izzy to pursue art. Liza was pretty skilled herself for her age. It also helped that unlike her teachers, Liza didn't see Izzy as someone who couldn't do anything wrong. And unlike Izzy's parents, she wasn't super delicate with her.
When Izzy went to Sterling C Royce, she tried to maintain her friendship with Liza. But things just kind of fell apart. They still regard each other fondly, but they didn't see each other much anymore. It ended the way a lot of these things end. But at least they had their time together.