He Proffesor,
In Thailand it is very easy to get a motorcycle drivers license, and I recommend that all people try to get it... Forget Thai riding schools, or something similar, the actual exam costs is something less then 200 Baht. With the rent of a motorcycle maybe 300 Baht. You can do multiple exams and still be cheaper then doing any training...
The Thai traffic code is old, and not so long ago the Thai government was thinking to split the drivers license for motorcycles into two, being below 250cc and above 250cc. But with the many political changes in the last few years I have the impression that this is not a high priority. So for now, if you finish the drivers test and get the motorcycle drivers permit you can step onto a 1000cc road devil and ride it legal. No displacement, learning, or horses limitations.
For the Yamaha Tmax 250, which I love to ride, it is a magical machine, still with the Thai price of plus 500,000 Baht you can get a few machines which also make you very happy.
Learning process of a female on a big bike is for everybody different, my girl's first motorcycle was a BMW 650cc Xmoto, it was her dream bike, so what could I say.......