Anything that your friend can do to make her migraine go away, particularly if it works nearly every time, is completely fine. That said with proper treatment from someone over a period of time in many cases you can make migraines go away permanently with no further need for treatment. In other words, unless it is your only option, do not be satisfied with simply managing the condition as it is treatable.
Now to answer your question more specifically, I'm not aware of what points you are using specifically. However, off channel (or pressure sensitive) points are commonly used in acupuncture also listed as "ashi" or "ouch" points (i.e. needling where the patient says palpation is sensitive). My guess in your case is that you are getting close to what would be the jing well points (the start and end of various meridians found near the nail bed) which are often used to clear heat and excess activity near the opposite end of the channel. So some on the feet like the liver, stomach, gall bladder, urinary bladder, etc. can be used to clear excess activity in the head/eyes/face.