I don't know the USATF process these days, but the 4X400 and 4X100 relay pools came from the top 6 finishers at the Trials in the 400 and the 100.
They would also open it up for other members of the Olympic team from another event.
If she doesn't make the 200m team and doesn't run the 400 or 100, I don't see how she gets placed on any relay team.
In 1992, Michael Johnson only ran the 200 at the Trials (and won that).
At the Games he did not make the 200 finals because he got food poisoning.
I remember their was controversy because it was announced Michael Johnson was not on the 4X400 and they would go with the top 6 from the trials.
But Danny Everett got hurt in his 400m prelim and could not run.
So, the replaced him with Johnson in the prelim and in the finals they kept Johnson in over Hall and Jenkins (the 5th and 6th place 400m finishers at the Trials).
All six (Johnson, Hall, Jenkins, Watts, Valmon and Lewis) received a Gold medal. The team in the finals broke the world record.
Everett did not, since he didn't run either of the 4X400 races. Though he did have a relay Gold from 1988.
I guess I went a little deep on the history but my point is, I don't see how Felix has auto anything before running any trials.