Hi Ceemee:
I've come to the conclusion that although I am not a full fledged N, I do have N tendencies that are sometimes healthy and sometimes unhealthy.
Welcome to the club.

My mantra of "Just get over it!" is not a cure all and can even be harmful depending on the individual
.
Being straight with you here......this is not any kind of cure. It's inconsiderate and unfeeling. So glad that you have recognized that it can be harmful. My bet is...it almost always is harmful to whoever it is said to, unless that person isn't listening.

I am glad to hear that you have made peace with your mother. I bet that has taken some very serious soul searching. And your concern for your younger sister is very loving.
I have reacted to my sisters present state by distancing from her as well letting her find her way and defending my mother as necessary.
Did you distance in an attempt to allow her to be an adult, or as a way to avoid hearing about her feelings about the abuse she believes she sustained?
In defending your mother, did you deny the abuse?
You may not have realized this contribution to her pain?
Am I wrong to think she needs my help?
It is never wrong to think. For the record, I think she needs your help but.....what that help is....may be arguable.
Does this situation sound healthy to you?
Between her and the pastor/wife? Sounds like a person was lost who went seeking surrogate parents and found them. Trying to heal the pain of the past by these relationships? Are they appropriate people for this role? Scares the begonias outta me.

They could be honest, caring, generous, giving people who have taken her under their wing and truly wish to help her......
or.....they could have nasty motives that only our worst nightmares might depict accurately?

If she is in danger,
Only your hair dresser knows for sure....but......it certainly smells bad doesn't it?
... what can I do to reach and help her?
Can you let her know first and foremost how much you care about her? If not in person than possibly in writing? Without judgement on her current behaviour, or advice, or even voicing your concerns? Just communicating that you are here for her, love her, think of her often, wish you could spend time together, would like to listen if she wants to talk about anything, miss her etc.
People make their own choices. It's so very hard to watch someone make what we think are big mistakes, isn't it? But really....what can be done? We are only in charge of ourselves. Trying to convince her that this relationship is screwy will probably only distance her more from you, this time by her choice. Suggesting anything, before trying to get closer to her and letting her know, possibly over and over, that you care....is probably futile too. She will need to really trust you before she will ever listen to anything you have to offer, I bet.
Do you take advice from people who distance themselves from you and deny your experiences?
Your honesty in all of this is so admirable. I wonder if you realize how brave you are?
Hope this helps a little.

Sela