I would advise self learning with astrology until she has a sense of her own approach/way with astrology, because it is a very personal medium. Every astrologer brings their own self, their own creativity to astrology and it's good to develop that before doing a course - develop your own ideas first in a nutshell. This was my experience anyway - when I did take tuition I was able to maintain my own approach while learning more of the theory/traditional techniques, and sometimes I had to disagree and say, no, this goes against how I experience astrology in daily life. It's a balance really, with the theory, because you need it but you don't want it drowning out your own gift or insight.

I learnt astrology using astro.com, books, the internet, and most importantly, observing, studying, researching and asking people questions ALL the time. Plus nature - it's a natural phenomenon so connecting with nature as it aligns with astrology helps (i. e., seasons, moon cycles, equinoxes, eclipses, star gazing, etc, etc). 

Start with "The Only Astrology Book You'll Ever Need".

Stupid title but a solid intro to all aspects of astrology, in small, understandable, intriguing bits.  It's easy to digest but correct and gives a person a good clue the vastness of astrology without overwhelming.