If Starfire were to get into a fight who would you think come out victorious? I’m being completely unbiased when I say this… but I believe Donna will win. Donna was trained since a child by Donna, she was also made to take down Diana. She also went through many buffs throughout the years it just makes since she can beat Starfire. Also if I recall in Titans Rebirth #16 there was an alternate universe Donna who gave the Titans a run for their money and it took Donna to take herself down.
Also similar thing happened in Return Of Donna Troy she was literally tossing the Titans around then. She even had a battle with Starfire in there and Cass said Donna was going to kill her if they did not stop her.