Long term relationships and Marriages borne out of affairs succeed less than 5% of the time, I have read as much as less than 1% of the time by some analysts...

Her excitement for this man will die at some point, and his for her likely even soner... and THEN the only thing keeping those two afloat will be their maturity level... They are on a sinking ship rotting at its core... they will fail.. it may take a while, but it will fail, they always do.

Don't worry about how you LOOK when the people looking at you are a bunch of ignorant children who enable infidelity and even celebrate it

You can thank Hollywood and the misic industry for romanticizing excitement and passing it off as "happiness" for decades.. the market is rife with that nonsense...

Serendipity
You've Got Mail
Sleepless in Seattle
Wedding Crashers

These films ALL ENDORSE sacrificing security and history for imipulse and excitement.. ironically they HEAVILY DOWNPLAY the waste and damage resulting from this escapism, and even try to pass it off as if it doens't do any damage at all...

These people you are surrounded by were educated on material such as the above... dont' expect respect from people so ignorant as ot believe romantic nonsense like that. You are tossing pearls before swine.

The purpose of maintaining a hold of your integrity is not for public appearance so much as for logn term peace of mind. If YOU WARN her and it fails three years from now, then you can rest at night.. if you don't warn her and even sign off on the escapism telling her you want her to be happy... when it failes, YOU will be implicated in her failure because you endorsed it.

The best think you can do is maintain your integrity and issue a solid warning and then GET OUT of the WAY.

Her entire social circle is enabling her addiction rather than supporting her in ending it... You can't fight city hall.

Once the addiction does end, and it will... THEN you can tell her "I told you so"...

The best way to respond to her infidelity is to hold onto your integrity like a lifeline and find peace in your life without her until the plane lands.

If at THAT time you DO want her back, tha'ts your choice, but I would NOT reccomend it withotu a VERY careful look at her lifestyle and social circle at the time ... if she is still acting like a teenager and hanging around marriage-threatening people then you know the risk YOU are taking full well then.