She has been flanderized from a nice, understanding, caring alien who secretly has a crush on Robin, and a cute badass to a psychopathic annoying "LOUD" alien cat person as she goes through derailment.
Annoying performance from Hynden Walch as she shouts 1/2 of her lines when portraying Starfire. What also doesn't help is that Hynden Walch is her original voice actor.
This is especially in the episode "Permanent Record", where she becomes a "grammar teacher".
She's prone to flip-flopping from being good-natured to getting triggered on the flip of a dime.
She's an insensitive jerk, carelessly assaulting the other Titans. In the original Teen Titans, Starfire never had destructive rage; however, in Teen Titans GO!, she does.
To be fair though, it is understandable for her to be violent since in the original DC comics, Tamaranians are a loving species but also warriors, and violence is more than acceptable to them.
Unlike her original series counterpart, her voice is pretty irritating, speaking in an ear-piercingly loud high-pitched register that is accompanied by broken English especially when she cries and when she says "Oooh!".
She is needlessly ruthless and abusive to Robin, who only wants her affection and attention. Though to be fair, she does have the right to be ruthless to Robin (the TTG version) since he’s overly obsessed with her.
She has an unhealthy obsession with cats, becoming a clichéd crazy cat-person because of it.
In the episode Flashback, she deliberately swallows a cat because her Tamaranian friend told her that cats are an Earth delicacy.
In the episode Starfire the Terrible, she is at her worst as she wanted to be evil and committed crimes because the other Titans only laugh at her, telling her she is too nice to even become a villain (which seems like more of a compliment than an insult), as she destroys Robin's hair gel (while trivial), destroying the moon with a toaster because she knew Robin likes the moon which was a stupid reason, she even throws the Titans (except Robin) down the pool of eating sharks without showing any remorse which is pure sadism, making her out of character.
Like the other 3 Titans, she becomes a brainwashed pawn to Brother Blood's fortune cookies and just obeys them without hesitation due to being useless without Robin's leadership and thus went to far by attempting to kill Robin without mercy in the episode Accept the Next Proposition You Hear.
As of right now, she has become rather dramatic by force.
In the episode, Bucket List, she, along with the other Teen Titans, childishly and stupidly abused a helpless baby (A REAL BABY) by throwing, pulling, and tugging her around like a rag doll. She eventually throws the baby on the bus, which is worse than the other Titans’ actions and she was praised for her behavior.
Hypocrisy: In "The Hive Five" (episode), she gets mad at Jinx for "engaging in the criminal misdeeds", despite that she has also done crimes herself or with Jinx.