In Avengers: Endgame, on Morag in 2014 after retrieving the Power Stone, at the instant she is meant to beam herself back to present-day Avengers' headquarters, Nebula is linked to the 2014 version of herself and realizes with horror that Thanos now knows of their Time Heist plans. However, rather than sending herself back to the Avengers in 2019, she runs to her spaceship and attempts to send a warning by radio. She is captured by Thanos, who then uses her knowledge, part of her head plate, and her Pym particles to engineer his final battle.
Why did she try to radio rather than just returning and delivering her message in person?