Having both of them survive is just a bullshit fan theory that allows Matalas to have his cake and eat it. If he wanted them to survive, why kill them off on screen? Ro’s death was perfectly legitimate dramatically, and it was very final.
But Shelby’s was just a cameo and meant nothing, which is maybe why he’s pretending she might have survived. It’s the same throwing away of characters for a cheap shock that was criticised in PIC S1.
Personally I don’t mind that she’s dead, but he should stick to his guns rather than comfort fans with the reset button. If you kill a character for a good reason you should stand by it. No backsies.