Velma Kelly is a jazz singer with enough attitude to commit double murder and still kill it on stage minutes after washing the blood from her hands. Not only that, she has the guts and the talent to turn a duo into a solo and bring the house down. "Don't sweat it, I can do it alone," she says to the club owner after killing both her partners—her sister Veronica and her hubby. (They were, um, keeping it all in the family.)
But prison wears down Velma's resolve. In prison she has to depend on others—paying Mama to make phone calls and paying Billy to find her innocent at trial. Initially, she still has the rude, swollen headed attitude of a star too big for her britches… almost literally. When Roxie innocently asks Velma for advice after washing her delicates, Velma snarls at Roxie, "Keep your paws off my underwear." Yet she later has the gall to complain no one has class anymore. Talk about irony.
Sister (From Another Mister) Act
As Velma's career rapidly disintegrates, Roxie's takes off. Velma realizes she needs to hitch her rocket to Roxie's star, so as the bandleader announces, she performs "an act […] of desperation" practically pleading for Roxie to team up with her.
Roxie declines giving Velma the same attitude Velma gave her when she first got to prison, and then some:
"You're all washed up, and it's me they want now. And I'm a big star. Single. […] Oh, I almost forgot. You were in the paper today too. In the back. With the obituaries. Velma Kelly's trial has been postponed indefinitely. Ohh. Seven words. Wow."
She knows right where to hit Velma: in the celebrity.
Mama sympathizes with Velma:
"These days, you get a little success, and it's good riddance to the people who put you there."
Not that Velma had any direct involvement in Roxie's success… but Mama will sympathize with anyone for ten bucks.
But after Roxie's trial, and she and Velma are in the same place: nowhere. Both of them realize they "can't do it alone!" which is quite a change from Velma's cocky attitude at the beginning.
When both women are equally desperate, they team up. But we bet that as soon as their career takes off (if it does) they'll go solo faster than you can say "shooting star."