It definitely depends on the system. Obviously, she's likely to get more out of a pension if she's not missing 10 years, however, that doesn't necessarily mean she'll have to work 10 years longer just to get a pension.
My minimum retirement age is 57, as long as I have 25 years in, so I have to work until age 57 to get my full pension, barring a special event allowing me to retire earlier without being penalized. At 57, I'll have 36 years in, so I could leave for 10 years in the middle, and still retire at 57, but I'd lose 10 years of my calculations (.1% of high three x # of years served).