a provider who has the same phone number on all directory listings including her website but...the phone number she supplies is different.

I am not a newbie here but thought this would be the best forum for thoughts on the issue.

Not unusual, at all. Most providers I know have multiple #'s.
As long as she is reviewed and established, I would not give it a second thought.

Many providers have someone else answering their website/ad number or going to voice-mail while using a different phone for those she wants to talk to.

If you were able to contact her via the phone number you saw everywhere and she has TER reviews.  I wouldn't be too concerned, but would still do a check of the new phone number on various places to make sure it doesn't come up with a picture of someone different.