Depends on your tendancy or anarchist sensibility.
Anarcho-syndicalist : "we'll talk about that together at the next department union assembly. By the way : have you payed your contribution this month ? ".
Anarcho-insurrectionnalist : "I usually don't consider honesty as a revolutionnary value... but, this time my friend, you've been too far"
Anarcho-primitivist : "I consider dichotomies such as "honesty/dishonesty" or "good/bad" as a part of the symbolist langage system of domestication. But this time you're pissing me off dude".
Anarcho-communist : "You liberal !"
Anarcha-feminist : "work on your shit !"
Anarcho-marxist / Anarcho-maoist (yes, they actually exist): "make your self-criticism comrad !"
Anarcho-nihilist : "You leftist bastard ! You still have illusions about changing society ! Ha !"
Veganarchist : "you're worse than a nazi butcher !"
Eco-anarchist : "You're infecting my biosphere bubble"
anarcho-individualist : "Dude : you're oppressing my Self, in the stirnerian meaning of the term"
- Kidding aside, I think that anarchists comrads or compas -of any tendancies-, most of the time -or at least too much often- try to mix ideology with trying to solve inter-personnal conflicts. When it's about oppressions like sexism, or essential contradictions or discrepancies, it should be revelant to try to ask the question of the best anarchist way to deal with it.
But I've seen this too many time, and I think it's also poisoning many friendly relationships : trying to transform any trouble or divergence into a civil war. And it could sometimes (if not often) come to the point of such examples I give above (according to each tendencies ;-) ). Maybe some people would see what I mean.
I think that we should try to avoid drama, and not transforming any broken promise or lack of honesty into a serious political problem, or a social catastrophy. Because there is enough of this all around us all the time, and between us.
Maybe we shall just rely on the simple anarchist principle of free association : social relationships based on long-term or ephemeral affinities, and build on reciprocity and undone -or temporary broken- when one of the individuals feel that he can't find the reciprocity, enough affinities, or what he/she was expecting of this Relationship.
So I think it also depends on the nature and "intensity" (which is very subjective) of the dishonesty. Like if you considere it "forgivable", or that it's too serious and puts you in an "alienated" situation.
Precisely, maybe there are some ways for trying to avoid authoritarian methods of solving such problems, for example in trying not to mix too much of anarchist theory in every aspects of our lives. But just behave like usual human beings. I mean : how do non-anarchist humanbeings to manage to solve such situations without being authoritarian douchbags and preserve their friendship ? I think this should be another radical way to ask it ourselves.
But, as a conclusion, always remember that only a friend can really disappoint you : because he/she's the only one you considered really trustworthy, and whom you were confident with.