She just tries to go and make decisions based upon her gut feeling, because she really has no past.
I mean, physically, obviously, you have the tattoos, and somebody clearly abused her.
It seems fair to assume then that Sif will at least have a larger presence in the film than the Guardians, but fans will probably have to wait a bit longer find out exactly what her function in the film is.
Fortunately, new signs suggest that Thor: Love and Thunder could feature the fan-favorite character more prominently than any other Marvel film has thus far.