There are two important points to consider that have not been emphasized and are critical to the success or viability of this decision. Neither is directly related to her gender or the structure of your relationship. They are:
1 - What type of person is she?
Is she a sensible, reasonably disciplined individual who is unlikely to do something impulsive and stupid like driving impaired or driving too fast and beyond her ability in a small, light, powerful car that she has no relevant experience in?
2- Is she conscious of and able to live with the reality that a Cobra is a loud, hot, smelly, and primitive little car whose only concession to creature comfort is a thinly padded seat?
It will blow your hairdos to smithereens and assault you with noise, heat, wind blast and the smells of gasoline and exhaust - and that is only when the weather is perfect. When it isn't perfect, you'll also be treated to sunburn, windchill and being soaked by rain - even when you choose to use the rudimentary and crude, awkward little soft top and fussy, pop-in side screens. A Cobra's idea of climate control is a gradual warming of the atmosphere with radiated heat and burnt carbon emissions.
Regardless of the weather, the sidepipes will burn you painfully and repeatedly until you achieve an uncanny, zen-like state that keeps you conscious of the pipes in relation to your body parts anytime you enter, exit or move around the little monster.
If she is both of the above and a true lover of sports cars, then the entire progression through choosing, buying, finishing and driving a Cobra will be a fantastic, rewarding process that will get better and better as you grow in experience, skill and familiarity with the joys and quirks of these unique cars.
If she is neither of the above, then the entire experience will be at best a frustration and a massive disappointment. At worst it will be a real disaster waiting to happen no matter what driving school she attends or how many yards of chromoly tubing are built into the integrated roll cage.
I say unto thee - know thyself and thy Cobra and thou shalt indeed be rewarded. Know them not and verily verily verily the nasty lil' beast will rise up and bite thee in thine arse.
Have fun and good luck!