Questions: Relationships

I am unsure of this myself.

I guess it really depends on the matter like if it's a relationship thing, for example:
A woman wents out with her friendly male coworker to have lunch together, she later on gets asked about her day by her boyfriend, she says what food she had for lunch but DOES NOT mention going with her male coworker to avoid a possible fiasco.

• Is it lying in this case? It is withholding an information after all.
• If she'd tell she went with a FEMALE friend to avoid problems, then that IS lying.

Neither is good though, I try to be honest as much as I can with my partner (when I have one).
Men aren't always willing to listen though, and they start making assumptions even when you are honest like when you tell them about the lunch with a coworker. Maybe it's an insecurity thing? It's def. common!

Do you find yourself crushing on another woman whilst married? How common is it?