Her reality consist of the family and the house, as Bob is experiencing the culture of Japan and feeling alive connecting with this young vibrant lady .. she has difficulty relating to his experience.
I though she was still doing her best to be supportive and understanding that he has to do this to provide for their family.
-It's only after we've lost everything that we're free to do anything-

Bob is clearly struggling with his responsibilities to his family despite his best intentions and so is Lydia.
Bob is successful and his work draws him away from his wife and kids. His wife cares for the homestead and has grown insulated, pragmatic and resentful of what she views as Bob's "carefree" life (repeatedly emphasizing that he continue to "have fun", to the point Bob feels he must correct her, in their brief phone conversations). Bob is not out galavanting, nor is his wife a shrewish caricature. While the alien setting on the protagonists refers to the films title, healthy communication between the Harrises is pointedly Lost in Translation.
This relationship was subtly handled and very insightful - part of the strongest directing in the film. The conflict between Bob and Lydia is both stated and implied in consistent ways which affect all of the rest Bob's interactions in the film, primarily with Charlotte.

Maybe she was a caricature? Maybe a balance to highlight the Bill Murray character? Maybe she felt alone and deserted while her husband travelled around the world on what, for all she knew, was a series of fun gigs while she held things together at home?
That's a crude word you used. Try something better next time.

and that, my liege, is how we know the Earth to be banana shaped.

That's a knee-jerk and, frankly, misogynistic take on Lydia. We don't see or hear nearly enough of her to make that judgment.
Re-watch the movie: Bob is NOT a nice guy for most of the film. He's sarcastic, smug and condescending. He also seems depressed (which isn't his fault, of course). They're clearly both sick of each other, and neither comes off particularly well in the conversations they have.
And do you really think that was the first time Bob cheated with all the traveling he did? Doubt it.

I always viewed it exactly like this. She was likely left alone a lot with what sounds like small children and an emotionally and physically distant husband. Who can blame her for not being immediately receptive to his newfound interests and he drunkenly slurred them to her. He probably shows little interest to her and the kids when he is home,so it probably bothered her to here of how much fun he was suddenly having in her absence. For the record,I love the Bob character but I can certainly understand Lydia's perspective,correct or not.

Don't be so quick to judge!
It appears that once they had children, his wife became the responsible one while he continued to travel doing his actinghe was never home.
I think she accepted her position with both the kids and with Bob,
I'm sure Bob was no "Prince" when he was home.
I also think that Charlotte has had an affect on him and during phone calls with his wife Bob is trying to be a better man/father/husbandwhich has Lydia scratching her head and is not receptive.

I think she poisoned the kids toothey didn't want to talk to him on the phone

The scene that got me was when Bob told her he really liked light Japanese food and Lydia tells him, "Well maybe you should stay there and eat it."
I mean WOW! What a b!tch

Yes.. all she cared about were material things, and ragging on Bob about how he's a neglectful father and husband. Not a nice woman at all.