Not enough information here to give a specific answer but:
1. You were married in 2015, so you file married for 2015. Sounds like you're filing married-filing-jointly, which is usually the best way. We're talking about IRA deductions, which are basically eliminated entirely if you file separately, so no point in even discussing that option.
2. There are potentially a few different limits that could come into play here in regards to tIRA contribution deductibility. It is a situation where you look at the same MAGI (Modified AGI) for both of you, however you might be applying a different limit for each of you.
https://www.irs.gov/Retirement-Plans/IRA-Deduction-LimitsThe simplest is for you - we know you have a 401K at work, so you compute your joint MAGI, and if it is less than $98K, you can make a full tIRA contribution. Up to $118K, you can make a partial one.
For your wife - if she had access to a retirement account at work, exactly same boat as you. If she did not have access to a retirement account at work, she can deduct fully at a joint MAGI of up to $183K, phased out to $193K.
So if your MAGI comes in between 118K and 183K for 2015, you could be in a situation where a contribution to her tIRA is fully deductible even though one for yourself would not be deductible at all.