The OP clearly says that a group of twenty 18yr olds (young adults), were looking for young juvenile catholics, to physically assault (or worse), that her answer/ silence could have caused her two protestant friends to be physically assaulted also (or worse),
As the OP has stated in Northern Ireland, violence between catholics/ protestants is still ongoing,
Such as one side beating/ maiming/ killing others because of their religious denomination.
No one is bound to reveal the truth to someone who does not have the right to know it. (CCC 2488–2489)
2488 The right to the communication of the truth is not unconditional. Everyone must conform his life to the Gospel precept of fraternal love.
This requires us in concrete situations to judge whether or not it is appropriate to reveal the truth to someone who asks for it.
2489 Charity and respect for the truth should dictate the response to every
request for information or communication . _
The good and safety of others, respect for privacy, and the common good are sufficient reasons for being silent about what ought not be known or for making use of a discreet language. The duty to avoid scandal often commands strict discretion. No one is bound to reveal the truth to someone who does not have the right to know it
Catechism says, if faced with people demanding truth they have no right to, to respond with silence or discreet language.
Silence would not have warded off suspicion from this adult gang that were preying on juvenile catholics.
A very careful answer was needed to this adult gang, the slightest suspicion in them, that they had found a young juvenile catholic to prey upon, could have had disastrous consquences, (they may have been very violent/ murderous)
Can anyone recommend what discreet language reply would be in keeping with the Catechism’s recommendations of with-holding the truth from those not worthy of the truth,?
Many Catholic Priests and Lay Catholics, went undercover to hide their identities during Nazi occupied countries during WW2, in order to live, avoid execution/ concentration camps, to continue the work of Christ in secret in Nazi countries, and to free as many jews/ christians/ catholics, to secret safe houses, and to safe countries,