If your wife has worked using SSN then you can't hide it... Even if you hide, if they later find out you'll be in trouble. It's most likely that they will not care that much of the work but hiding is bad.
It really depends on how tough the immigration officer is. It's about luck.

Has she gone to Nepal after that and re-entered US in a valid non-immigrant visa  ? If she worked during F1 and she went Nepal and came back to US in H4 then that should be fine. Like I485 mentioned above, after she enters US on a valid non immigrant status USCIS can't go prior to her last lawful entry. Otherwise they have the right to look 5 years employment history and do background checks.

In the end, USCIS most likely won't deny I-485 for such things but that's how everyone thinks until someone experiences that.

Find and immigration Lawyer and explain all these things. He/she will be able to tell you what to do and what not instead of asking questions in sajha.

Just because someone in Sajha says don't mention that work history , you'll be fine doesn't mean you shouldn't. You should take steps so that if you're that one unlucky person your lawyer maybel able to handle that case nicely later on. That's the reason why we hire Lawyer.

One more thing: If she's still working I would avoid doing that during the I485 process just to be on safe side.

Good Luck.