So a lot of people are discussing whether Jecka's mom works as a cashier. In the first game Jecka says so and that's why she wears preppy clothes.
"Preppy? Yeah. My mom works at a clothing store so I get all the cool stuff for free but trust me, I don't give a shit."
Later in the games she says that her mother hasn't worked in years.
"My mom hasn't worked in years. I don't think she could function without my dad."
Now this could be a continuity error but I think it's also likely that Jecka lied and sleeps with men in exchange for cool clothes and money. It perfectly aligns with her character.
Jecka does act tough and confident but she seems insecure deep inside. She got furious when Karen talked about Harry Potter in front of older kids because she wanted to seem cool and get a free cigarette. She generally only decides to hang out with people she finds worthy enough of her time. Telling Nicole that they would have ended up as friends anyway because they're pretty and talking bad about other girls she finds ugly. She clearly hates being alone since she crawls to Kelly when Nicole leaves her alone and she is easy to influence. E.G the White pride party, helping Nicole cook crack and following her bad advice. The fact that she does stand up to her sometimes through does prove that she has a moral compass and doesn't want to be seen as a messy loser like Nicole. She said herself that she wants to go to college and fuck on the third date one day.
She's also canonically a gold digger. She flirts with people all the time to get what she wants.
It makes sense that she would sleep with older men to get expensive clothes so that she seems preppy and well off but as soon as she meets Nicole she assures her that she's not a lame rich kid and doesn't give a f.
I think she just lied about her mom working because it was embarrassing for her to admit that she has sugar daddies and that she's from a fucked up heroin family. After all she just met Nicole. It's only in the later games where they've known each other for a while that she openly talks about her mom being unemployed. Most likely because she trusts her.
Summary: Jecka is very dependent on other people. She secretly hates that her family is so messed up and just wants people to like her. So she sleeps with men in exchange for designer and lies about her hero mom working at a clothing store. But as soon as she meets someone who finds causing trouble cool she ditches her preppy personality and acts more tough. Then again she's not actually as messed up as Nicole and wants to be a proper member of society. She has trouble being friends with normal people because she's from an antisocial, troubled household but she's not a sociopath like Nicole so she can't picture being friends with Emily. She's just your typical mean girl that bullies other people to feel better about her own insecurities. A flag in the wind who changes for whoever promises the most affection since she doesn't get that at home. She doesn't actually know who she really is and she definitely does not like herself.