The Maga--if that's what she is--could have Immortality of the Forest, from "Guardians of the Forest: The Rhine Tribunal". It would give her a total Warping Score of something like 24+, however, it is actually possible for one to survive this provided one stays clear of Twilight.
Despite what the texts suggest, a very determined mage can avoid Twilight by building up knowledge of Vim and Concentration, cultivating a very strong Familiar Gold Cord, and performing magic only in low-Aura areas, with an emphasis solely on Mastered Spells. As long as the mage doesn't experiment or take any magical risks, immense age is possible.
Without Immortality of the Forest or undergoing some manner of Mystery, the most likely upper practical limit of a Maga's age would be around 500 years. Allowing for a full set of bonuses from a Bronze Cord, a Summer/Autumn Covenant in a healthy environment, one could add an extra +9 (bonus inverted) to Aging rolls. With a dedicated Longevity Ritual designer working in a team (and probably having a Magical Focus) another +40 (Longevity Ritual 200) could be achieved. Of course, there'd be the Twilight avoidance problem, but this would still be within theoretical reach.
At even 500, one has to wonder how/when she joined the Order. The amount of Pre-Hermetic knowledge which she would possess would be awesome. More than enough to earn her a place as perhaps the most revered Seeker in the Order, or the Prima of Ex Miscellanea. Would she be viewed as a "Hedge Wizard", however, since she predated or was contemporary with the Founders?
It's worth noting that Unaging combined with the conditions stated above--and Strong Faerie Blood if one has it--can allow one to avoid undergoing a Longevity Ritual until one is well over a century old. Depending upon how lucky one is with the die rolls, one can push 150+ before the creeping approach of Decrepitude (2+) forces a Longevity Ritual, though one should always have a CrCo 40+ Ritual ready to deal with an Aging Crisis.
On a related note, the annual "2 Warping per year" average presented for Detailed Character Creation is really more like 1 per year, with another gained for the Longevity Ritual. So those Magi who don't use Longevity Rituals for their first century or so have an extended career and life expectancy. One should see more of them in the Order, as the demographics would begin to favour them, particularly in positions of power.