Well, now Alien Amnesty would give her a pathway to citizenship. Boom. Legal.

Here's what I think is the deal. The government gave her the identity of Kara Danvers, the daughter of whatever their first names are(can't remember right now and I'm not looking it up), Danvers. They gave her a false identity complete with Social Security Number, birth certificate, etc.. Remember, in the show the DEO was set up as a result of her being on earth and the other aliens that showed up. The government has known about her since she arrived and has been monitoring her.
So, she would be able to go to school,get a job,open her own accounts,get a driver's license,credit cards,etc., as Kara Danvers with no issues. Now when she's in Supergirl attire IF she needs to purchase something she can always use cash which she probably carries in her pocket.The suit probably has pockets. You don't need to give them your name to make every day purchases. And when she's dressed as Supergirl her name is Supergirl. She probably gets stuff for free as Supergirl anyway. After she's saved people's lives I'm sure they're grateful. Anyway, it's a fantasy show. The less you question the more you enjoy it.It's a nice break from reality. Thanks for the question though. I think it's funny and cute. It's fun to think about and come up with our own theories to fill in the gaps left by the writers.
This. LOL
"I'm the ultimate badass,you do NOT wanna f-ck wit me!"Hudson,Aliens

But what does she really want if everyone knows her secret? I mean everyone who knows her knows she's Supergirl - the scrawny Jimmy Olsen, the bulky Jimmy Olsen, her sis, the DEO hell even old cranky poodle like Cat. I thought the most cheesy superhero show I saw was Lois & Clark but this top that in every way. L&C: Season 1 was good cheese, this is just farts blown on your face.

Batman is who I am, Superman is who I want to be!

This has got to be the funniest thread I have read in a long time. Then again, I'm not on the internet much these days.
Here's what I think is the deal. The government gave her the identity of Kara Danvers, the daughter of whatever their first names are(can't remember right now and I'm not looking it up), Danvers. They gave her a false identity complete with Social Security Number, birth certificate, etc.. Remember, in the show the DEO was set up as a result of her being on earth and the other aliens that showed up. The government has known about her since she arrived and has been monitoring her.
So, she would be able to go to school,get a job,open her own accounts,get a driver's license,credit cards,etc., as Kara Danvers with no issues. Now when she's in Supergirl attire IF she needs to purchase something she can always use cash which she probably carries in her pocket.The suit probably has pockets. You don't need to give them your name to make every day purchases. And when she's dressed as Supergirl her name is Supergirl. She probably gets stuff for free as Supergirl anyway. After she's saved people's lives I'm sure they're grateful. Anyway, it's a fantasy show. The less you question the more you enjoy it.It's a nice break from reality. Thanks for the question though. I think it's funny and cute. It's fun to think about and come up with our own theories to fill in the gaps left by the writers.

Batman is who I am, Superman is who I want to be!

Well, that's called tyranny; and its generally frowned upon."

Presumably, the Danverses went through legal channels, just not telling anyone she was alien. If she's working for Cat, she's paying taxes. Her citizenship would automatically be assumed as a foundling.

Why wouldn't she carry cash? She probably has a hidden pocket in her uniform.
In the kingdom of the blind, you're the village idiot.

But what about a SSN? Is she a naturalized citizen? Does she pay taxes get medicare etc?

Batman is who I am, Superman is who I want to be!

Batman had Bat-credit card!

I guess the DEO has a bunch of prepaid debit cards for her. And a lot of places still take cash.

yeah but how would she use a creditcard? Or get one?

Batman is who I am, Superman is who I want to be!

If she was just Supergirl she would have no reason to hide her identity, would she?
.

Hmm, my point is if she was just Supergirl how would she buy groceries or anything?

Batman is who I am, Superman is who I want to be!

Well sometimes, in the case of her stopping the robbery at the pizzeria, they gave her some. Rest of the time she gets her food as Kara Danvers. And if she has to, carries cash. Some people still do that.

wth kind of topic is this
You can't persuade fanboys. You'd be better off trying to convince a wall. ~CodeNamePlasmaSnake~

She doesn't wear her Supergirl costume to go shopping. Really not that hard to understand.

Don't do it in uniform