These issues would be what may (and most likely would) hinder her progress:
Respiratory system: Marijuana can be especially harmful to the lungs because users inhale the unfiltered smoke deeply and hold it in their lungs as long as possible. Marijuana smoke can cause the same breathing problems that tobacco users experience, including bronchitis and emphysema.
Cancer: Marijuana smoke contains more cancer-causing agents than is found in tobacco smoke. In fact, studies show that someone who smokes five joints per week may be taking in as many cancer-causing chemicals as someone who smokes a full pack of cigarettes every day.
Reproductive system: Heavy use of marijuana can affect male and female hormones, diminish or extinguish sexual pleasure, and cause a temporary loss in fertility. Among other symptoms, women may have irregular menstrual cycles, and young men may experience the delayed onset of puberty.
Immune System: Animal studies have found that THC can damage the cells and tissues that help guard against disease.
I don't think it's really a very good idea if she wants good results.