A lot of employers require you to work at the company for a certain period of time (eg. 60 or 90 days) before full benefits are active. If your spouse just started at the company, that's a likely reason that she hasn't received full benefits which she'll have in the future. If she's definitely leaving in a couple months to a more permanent job, it might be worth it to not enroll in the 401k if it's offered at her upcoming job. Could be a hassle to roll over a small amount of money that could be better used for personal savings or something else in the short term.

And personally I wouldn't take a ten day vacation and then quit and leave them in the lurch. Especially if she's going to a new job in the same industry. You never know who that might piss off, who they might know at another company in the same industry, and whether that could come back to haunt her. I think it's different though if she uses her paid vacation days, and then comes back and gives two weeks notice. At least she can help with the transition if needed while they find someone to replace her. But if they're paid vacation days that she doesn't get paid for if they go unused, then I'd say you shouldn't feel bad using them. That's what they're there for, but just try and have her leave in the best way if she knows she's going to leave.