I would say Gamora was begrudgingly obeying Thanos rather than willingly. She was constantly searching for ways to stop the Mad Titan, especially by keeping him from gaining access to the Infinity Stones.
Her strategic subtefuge subtext can be viewed early at the 1:15.30 mark of
Avengers: Endgame, when Nebula accidentally projected a holographic conversation of The Avengers' plan to capture the stones--due to a crazy cross-connection between the future Nebula's and her past self's tech. Gamora tried and failed to throw off Thanos' curiosity by describing the event as a glitch.
In regards to Gamora #2, the audience must remember she was slightly older than the original one seen in
Guardians of the Galaxy Voi 1. She would have been even more cold and savage towards others than when she finally met up with her Scooby Gang. It would have been the only way to keep her sanity in check serving under Thanos.
As far as time travel in
A:E, I would recommend these video marks:
31.50 - Lang's rambling hypothesis of time travel
39.30 - Stark's proving Lang's hypothesis with a working time model (he is such a freaking super genius
)
59.23 - Banner's breakdown of the consequences of time travel
One important thing to remember. This was all time travel, not trans-dimensional travel between universes (although the time traveling was conducted
through the quantum realm). Gamora was from the past existing in the same universe, not from another universe. Just adding that for consideration before
The Flash debut. That movie will be about time paradoxes, which Stark was able to avoid with his big brain, lol.