how would you depict Star Girl meeting Super Girl or the flash?

Well, I'd love to write this scene, but I'd need more background on the character of Stargirl first. Does she know who Supergirl is? If not, that changes the entire scene, because it alters the type of interaction between them. I'll have to know more about Stargirl, too. I'd probably have to wait until I've seen a few episodes of her new show to get a feeling for her personality, specifically her quirks and manner of speaking (including any pet phrases).

I'm thinking and this is just an rough idea. that she cross over's with flash first. that same how she end's up on Earth prime. meet's Barry allen and they team up. Barry allen make's an reference to Kara Zor el. some thing like this.

Barry: I know some body else.
That wear's an out fit that has similar color's. except her out has red cape & yellow triangle with red S symbol. that also include's an pair of red boot's.
Counrtey: who's that?
Barry: Her name is Kara Zorel or know in National City.
As Super Girl. she has the power of flight
Counrtey: how can regular human being?
be able to fly?
Barry: she's an krypton ion. From an planet called Krypton.
then what I'm thinking at same point in the cross over. he just show's her an picture of Kara Zorel.

this rough idea for Star Girl and Super Girl cross over.
The twist would be having Kara Zor El going to Earth 2
I would have her fly through the portal and land in FRont of her.
Then have counrtey turn to comsic staff.
Counrtey: No, I 'm not
Going to wear a cape.

I don't oppose a Stargirl crossover, but I would have to wonder what the point of shutting off access to other universes was.

It would kinda feel like a cheat if they shuttered the multiverse just to open it back up so quickly. I'd like to see Melissa as Power Girl who could potentially reside on Earth 2. I had wanted her to be Power Girl on Titans or Doom Patrol or another DC show... it could work here. How about Grant as a descendant of the Earth 2 JLA Flash?

I gotta be honest. I don't have much desire to see Stargirl interact with Melissa Benoist's version of Supergirl. Maybe if our Supergirl was still her season 1 or 2, learning her way Supergirl. Now, though, with the age and maturity gap, I think I'd much rather prefer this alternative...

I'd love for Stargirl, through some alternate universe, time traveling goodness, to interact with a Izabela Vidovic's Kara. Maybe even introduce a universe where she's a fully costumed, younger version of Supergirl. I think the two, at that age, could have some truly wonderful interactions.

Everything I've read makes it seem like Stargirl kinda replicates that fun, joyous, happy-to-be-a-hero vibe that Supergirl had in it's first couple of seasons. I feel like THAT Supergirl would be a fun interaction with Courtney. But with how melodramatic and overly serious the series has become, I'm not sure it would quite mesh with our current version of Kara.

Unless...Stargirl was able to reignite that joy in Kara that she once had in her heroics, early in her career.

There is potential. I'm not counting on a crossover happening. But there is potential.

I think they would get along very well, with the same type of older/younger superhero relationship as Kara/Supergirl and Nia/Dreamer have. Both Brec and Melissa are sweethearts in real life,and their characters reflect that. And I think that Alex and Pat would also work well together.

As soon as I have time, I'm going to write a fan fiction story in which Supergirl tracks down Lex Luthor in Blue Valley, and unexpectedly runs into Stargiirl in action. (Courtney doesn't know who Lex is.) Then they join forces to defeat Lex and his cohorts in crime.Their first meeting would be basically the same as the Flash meeting Supergirl in the Worlds' Finest episode in Season 1, except that "ace reporter" Kara would likely be aware of reports of a new superhero in the area. And I would expect that Supergirl would be well-known enough throughout the country that Courtney would have heard of her, but she would still be shocked to find out that Kara = Supergirl.

I thought this may be of interest to this discussion thread.

https://www.tvguide.com/news/stargirl-brec-bassinger-supergirl-arrowverse-crossover