Kendra Quaker is the head cheerleader, the prettiest, most popular girl in the school, and one of the main characters in 13 the Musical.
Lucy is Kendra's supposed "best friend". Since Lucy likes Brett, she envies Kendra because Brett likes her. Due to this information, Lucy tries to snag attention from Brett and will do anything to get him even if it means backstabbing her own best friend. When Kendra has her date with Brett and it horribly fails, Lucy kisses Brett in front of her and Brett starts dating Lucy instead. After this, Kendra and Lucy have a catfight in the girl's bathroom. They aren't really seen much together after that interaction.
Kendra and Brett like each other. He asks her on a date to see the Bloodmaster and she happily accepts. They go on a date but the date goes horribly and ends up in Brett kissing Archie. Kendra wasn't totally sure about what was going on though. After the catfight with Kendra and Lucy, however, Brett gets back with Kendra. Kendra believes Evan set this up and gives thanks to Evan through a hug, Brett finds them and assume that they have been dating. Kendra then chases after him and it isn't known if they dated after that interaction.
Kendra isn't really seen with Evan much, but there was a rumor spread about them by Lucy that they were secretly dating behind Brett's back. Kendra thanks Evan for getting her and Brett back together and hugs him as an act of gratitude. The other kids find them hugging and assume that they were actually cheating. Kendra claims it was just her showing her thankfulness but the others don't believe it.
Archie has a huge crush on Kendra. Archie gives some encouraging words to Kendra ("I think you can do a lot better than Brett!") after Brett breaks up with her due to him thinking she cheated on him. She says thank you to him, but gets his name wrong, and runs after Brett. Archie calls her a moron, but in "A Little More Homework", after Archie says he got spinal cord surgery, Kendra stands next to him looking at him sweetly.
In the Broadway version, it is implied that Kendra (along with the other kids) does not like Patrice. In the Goodspeed version, there is a scene wherein Kendra and Lucy bully Patrice for allegedly listening in on their conversation.