Chances are if your friend is using marijuana too frequently, you already know it. For better or for worse, using marijuana is not really considered a problem, so even heavy users are not very secretive.
If your friend is using a lot, you may want to suggest she think about cutting back. She may refuse or just let out an amused chuckle, but you can ask her to take some time to think about it. If she finds cutting back is not so easy, you may want to suggest an assessment (when a professional counselor or doctor talks to a person about their drug use to determine whether or not there is a problem). Don’t just blow it off, or think it is no big deal. If you are concerned, there is probably a good reason for feeling that way. Trust your gut!
If your friend is willing to consider getting some help, you can call 800-662-HELP or visit www.findtreatment.samhsa.gov to find a program in your area.