^^^ I agree. Just tell your friend what you saw in a very casual manner. Let him draw the conclusion.
Ideal Situation:
TS: Pare, I saw your wife last night at * Hotel
Friend: Oh yeah, she was there last night helping out her balikbayan cousin check in.
Bad Situation:
TS: Pare, I saw your wife last night at * Hotel
Friend: Really? She said she was going to the mall with her friend. Who was she with?
TS: A guy
Friend: What were they doing?
TS: I just saw them check-in. (devoid of malice)