The "Tax deductibility of Traditional IRA contributions" table at your link is what you're referring to?
At the top of the column it says "IRA Owner Does Not Participate In A Retirement Plan At Work", so that would be true for your wife, as the IRA owner.
Then, assuming that you guys are Married Filing Jointly, the cell you're interested in says:
Spouse does not participate in a retirement plan at work:
No income limit for full deduction
Spouse participates in a retirement plan at work:
Full deduction:
MAGI less than $181,000
Partial deduction:
MAGI of $181,000 - 191,000
As it is written, your wife is the "IRA Owner" so that means that 'spouse' is referring to you. Since 'spouse does not participate in a retirement plan at work' isn't true for you (because you do participate in your 401k), then you have to keep reading further down to find the phase-out. If you're making less than $181k, then yes, she can contribute to a traditional IRA and you guys can fully deduct that contribution off your taxes. Phase-out sets in after that.
For a bit of pedantry ...
I want to know if I can change my contributions from a Roth IRA to a traditional IRA for 2014.
You can always contribute to a traditional IRA. You just may not be able to deduct your contributions when doing your taxes.
But I read if we are a single income home ...
It doesn't have anything to do with being single-income. It only has to do with (non-)participation in work-sponsored retirement plans.