Good for her for pursuing her passion. However, IF she's planning on doing print or runway modeling, not only is it a 1 in a million shot to make it, she's even more hampered by the fact that she's 6'4" tall. I don't have the stats handy but i don't think it's going too far out on a ledge to say 99% of the successful models out there are between 5'8" and 6'0" tall. At 6'4", she's WAY outside of the range of even the tallest models who actually work. Clothing designers generally make their garments for girls/women in that height range. She will find it VERY difficult to get any kind of work in that industry.
There are many types of models - those who model body parts (seriously), bikini models, and fitness models to name a few. She certainly could fit into the last category if she so desired...
If, on the other hand, she wants to pursue a career in the fashion industry, unless she starts at an internship through some great connections, her best bet IMHO would be to stay in college and get a degree in fashion design, or fashion merchandising, or some other major related to her passion. I don't know the specifics of her decision or what kind of modeling career she desires, but it's certainly a risky endeavor to give up a 4-year FREE education to pursue something with such a low probability of success. Then again, we have no idea what she's really pursuing so...
It certainly is an interesting twist in her "career" for sure. Going to be interesting to see how it turns out...