Ayurvedic medicine is not scientifically proven, although it is definitely being studied by the scientific community.
Perhaps the biggest problem with Ayurvedic medicine to date are reports of lead, mercury and arsenic found in some herbal preparations that were being sold in the U.S. and on international markets. Between 1978 and 2009, more than 80 cases of lead poisoning were reported in the medical literature in people who use Ayurvedic mixtures.
There are also potentially dangerous drug interactions with some of the herbal concoctions prepared by Ayurvedic doctors.
As this blog reports, the practice of Ayurvedic medicine is based on a belief in doshas - primary life forces - which they believe exist in every human being. (Belief in these universal life forces is part of a pantheistic world view that is not compatible with Christianity.) It is believed that each person is dominated by one of three doshas and that this dominant dosha is responsible for the person's physical, emotional and spiritual characteristics.
According to this statement by the American Cancer Society, practitioners of ayurvedic medicine diagnose patients by observing the body's nine "doors" - eyes, ears, nostrils, mouth, genitalia and anus - as well as their fingernails, tongue and lips. Through these observations, along with listening to their lungs and heart, the practitioner determines the state of these doshas. Treatment involves the rebalancing of these doshas so that the organs of the body can work together, and remain in unison with the environment and cosmos. Other factors, such as diet, relationships, emotions, lifestyle, and even the seasons and/or time of day are all factored into a possible treatment protocol.
Although some of the herbs used in Ayurvedic medicines have shown some promise in laboratory tests on rodents, there have been too few randomized studies on humans to make any determination about their effectiveness.
The religious roots of Ayurvedic medicine is evident in that it emerged from an ancient body of knowledge known as the Vedas. The Vedas is the same text from which India developed its moral, religious, cultural and medical codes, so it is not possible to separate the physiological aspects from the spiritual as the two are inherently intertwined - i.e., belief in the spiritual concept of doshas and its emphasis on the practice is yoga, visual imagery, meditation and breathing exercises.
However, science may find some usefulness in other aspects of Ayurvedic medicine, such as its emphasis on proper diet and exercise, or in any of a number of the herbs used in the practice - but this would no longer be Ayurvedic medicine. This is what is happening with acupuncture, as this blog explains.
Yoga is in a category all its own merely because most of the postures (asanas) are designed as positions of worship of Hindu gods. Yoga was never designed to be exercise but is a spiritual practice that westerners are trying to turn into exercise but are failing to do so because they insist on leaving the postures intact - much to the chagrin of Hindus who are furious at this defacement of their religion.
Your friend's belief that Ayurvedic medicine is supported by science is premature, but it is definitely being studied at the present time.