GLIMPSE OF REDEMPTION
Trigger An enemy attacks one of your allies or a creature
that’s friendly to you. Both the enemy and ally or friendly creature
must be within 15 feet of you.
The ally or friendly creature gains resistance
Trigger: An enemy attacks one of your allies or a creature
1) So does the reaction occur when some attacks an ally, or HITS the ally with an attack?
The difference being, if it's just an attack, what if it doesn't hit ? Then you would waste your reaction
2) Does a spell or breath weapon count as an attack for the use of the ability ?
1) Since the trigger is "An enemy attacks", a strict RAW interpretation would say it must be triggered when the attack is declared (aka before the attack roll but after the attack is announced).
2) I've been determining what counts as an attack by checking the action for the Attack trait - most area effects don't have the Attack trait, so I don't apply it against things like Fireball or breath weapons. Basically, if it requires an attack roll, it's an attack.