Unfortunately, psychiatry is self-regulated, and every state has slightly different regulations on what is needed, etc. So, it's hard to find a trustworthy website or reference place. That said, her best bet is to look into addiction treatment centers (that's what compulsive spending is, actually) and schedule a consultation. Most have free consult. She can google "Compulsive spending treatment" and her city and state, and that should bring up a list of treatment centers. She can check the BBB to make sure they've no complaints against them, and the state psychiatric board. Aside from that, the only option is to ask for referrals from friends, family, co-workers, etc. She is going to want to find an addiction specialist, but she may not need a psychiatrist. Many psychologists and behavioral therapists deal with these issues, as well, just as effectively. Behavioral therapy is one of the most effective treatments for addictions, so she may want to look up those therapists with a behavior philosophy.
There are often support groups, as well, and those can be a better source of referrals. Some are held like AA meetings, and others as group therapy sessions. She should be able to find those online, through the addiction treatment centers, or through her local health department. Other people in the same situation are likely to give her the most honest, useful referrals.
I hope our reader finds the help they need, and I'll be thinking of them today.
"This isn't life in the fast lane, it's life in oncomming traffic." -Terry Pratchett