I depends on so many things.
I would guess she can get another year or 3 out of her, but likely less than 5.
Is she coming from a commercial herd as a cull?
Her bone structure and the quality of care she has had will make evry bit of the difference.
Things to look at~
Udder condition:
How is her bag?
Does it hang very very low? Is it really lopsided?
Often older cows lose their center support and the teats stick out kind of sideways.
They are more prone to damaging them then.
If the back quarters are significantly lower or bigger than the front ones, that could mean she will be hard to milk out.
Over time their udders tend to sag.
With short cows, they can almost touch the ground when at full production.
Has she had mastitis?
Permanent scarring from mastitis infections?
Feet and hips:
Look at her hooves. Do they wear evenly?
Do her joints seem swollen?
Does she walk easy with her head at a natural angle? (that can be a tip-off for painful walking).
Any sign of lameness is an absolute no-go with purchasing an older cow.
Has she had milk fever in the past or any prolapses?
What kind of milk production is she known for?
Has she been fed and vetted properly all her life so far?
I would be extremely wary of buying a cow this old, unless you are getting a very good deal.
If she seems sound, has a fairly 'high' udder that milks easy and you can afford to gamble a little, then maybe.
Good luck to your daughter.
If it isnt THIS cow, then another one will come along for her.
Tell her to take her time and shop around. Dont just fall for the first one she finds.