If the reviews are here on TER, there should be some type of information in the contact section of the profile concerning how you get hooked up with the provider.  Normally there is a phone number and/or an email address.  The phone number or email address will be to the Agency, try contacting them and asking for an appointment with the provider, be sure to give her name when asking about her.  If you are asked how you found them, mention the reviews (not in detail, just where you read them).
    Some agencies do require that you join (become a member).  I have no experience with ones that require membership to see a provider, I have dealt with some that have members but welcome newcomers who do not want to become members.
    Good luck.