The way you phrase the question sounds like you're misunderstanding how the 90-day rule works.
Even though the visa itself declares a "length of stay" as 90 days, this does not mean that the visa carries a fixed supply of 90 Schengen days and will be useless once those 90 days have been used up. This is indeed how it would work for shorter visas, but when the visa is valid for more than 6 months, the only thing that restricts the length of visits is the general 90/180 day rule, and the "length of stay" field is filled in with
90 as a reminder of this.
The 90/180 day rule is that on every day you're present in the Schengen Area, you must have been in Schengen for at most 90 of the last 180 days (including today). The EU provides an online calculator to help convert this rule to actual dates.
The 90/180 rule applies to everyone who does not have freedom of movement in the EU due to their own or their family's citizenship, no matter whether they are visa-free or have visas. (Aliens with residence permits or national long-stay visas get to count days in the issuing states as "not in Schengen" for the purpose of the rule, but their clock keeps ticking uninterrupted as regards the other Schengen states). It applies per person, and getting a new visa does not reset your running count -- the only thing that causes days to disappear from it is waiting for them to drop off the running 180-day period.
What this means in practice is that there's no reason for your wife to apply for a fresh visa. Assuming the current visa provides for MULTiple entries, getting a new one would not give her any benefit.
If all of her 80 days were in February 2016 or later, they will only begin to drop out of her running 180-day count around August, so the earliest time she would be able to start a one-month visit would be in late July. (Or even later than that if there were gaps between those 80 days).