It is impossible for the player character to fail the test. Unlike other settlements around the Commonwealth, Covenant is surrounded by tall concrete walls sprinkled with defensive turrets, and the houses and the yard are in pristine condition. The Sole Survivor even mentions how everything looks almost pre-War.
In my experience you dont have to even flirt at all to be able to romance. Once you reach the highest affinity with them they will initiate dialog fairly regularlly which will include the romance option again so if you fail you will get more chances.
No there's no way to fail it, just like everything else in the game handholding you.
If you are not worried about role-playing just let Amelia die. There are no repercussions for doing this and it keeps the settlement friendly.
Effect on Speech The final result of the Chance to Succeed formula is limited to a minimum of 5% and a maximum of 100%, so there is always a slight chance of success. One has a 100% chance of success to pass a Red check with a Charisma value of 11 or higher; this includes all clothing, armor, and drug effects.
Inside Covenant, players can find a few things that raise suspicions, like an abandoned bed roll, a note that talks about the rules of Covenant and how not to talk about Synths, and self-help books. Yet, none of this leads to concrete evidence of the fate of the caravan's survivors, or Covenant's involvement.
If you destroy the institute, the covenant quest chain no longer starts. You need to acquire the settlement earlier in the game.
IIRC the easiest way to do the quest is just to sneak into the house immediately to your left as you enter, steal the computer password from the end table left of the door, then go to the house at the end of the settlement, where you see the jail cells, and use the password on the computer.
Take The SAFE Test Players can answer these questions however they would like, whether their responses are cruel, compassionate, or neutral, it does not matter, as there is no way for players to fail the test.
Visitors to Covenant are subjected to a psychological test, called the SAFE test.