You are lucky. The brainwashing did not catch, but the same brainwashing worked on her. You are not going to change her, but you love her nonetheless, so nod your head, smile and bear it.

From the time I was 18, most of my conversations with my mother included me saying, "Mom, I love you, but that's none of your business." After about 15 years she gave up on trying.

Be strong

I'd guess she has a mental illness (beyond delusional belief in a fairy tale). Her abusive behavior is one sign. her desire to control you and her inability to listen/hear you are others. Try to make some sort of deal with her, like, if she goes to a therapist (not her pastor, lol), you'll match her by going to a Sunday serivce. What's an hour or so listening to stuff you already know compared to possibly helping your mom find some peace? Worst case, she refuses. Threatening a controlling person won't work, you've got to either cut it clean or try to make compromises when you see the chance.
Mainly, though, don't let her hurt you any longer. You took a huge step leaving, unfortunately, you might just need to ignore her for long stretches (or entirely) to keep your peace.

..and now she answers the phone with, "Praise the Lord" as if she's trying to push away a demon. It's getting worse and worse. She's really trying to make my life miserable again.

Never had to deal with that type of situation, must be tough. My grandparents were very religious but I never really brought up the issue. Except in some discussions with my grandfather, where he said that a person could not be good if they didn’t believe in god or Jesus can’t remember which. I disagreed to that and we just left it there.

I am in a similar situation, but my mother shows me some respect in part because she needs money from me from time to time. She sends me all these insipid religious messages on WhatsAp to the point where I blocked her. Once when she asked me for money, I asked her to pray for it because her god answers all prayers. Of course she didn't find it funny, but it gave me wicked satisfaction. These days, she doesn't talk about her god much.
Your situation is different, but to be honest with you at my age, 47, I have zero tolerance for intolerance regardless of the provenance. Good luck.

Just this past Monday I was having lunch at my parents’ and my younger brother was also there. Out of no where my dad starts thinking out loud and volunteers a fasting date for himself my mom and my brother, in hopes that it will tug at god’s strings and make me a believer again. I humorously said that it will most likely be in vain. I do sometimes have to be more stern with my dad and tell him to drop the subject when he brings up religion/belief.

Is your mother... I was about to make a post how I just befriended My Ordered Minister Older Sister in Facebook... with everything that it meant and the aggravation that will bring... but is my Older Sister... she is part of me as I am part of her. Our best memories are teen memories. That won't change. Treat your mother with respect even if she don't treat you with the same respect... She will one day Realize How Good of a Daughter You Are. My ex wife always end our conversations with "god bless you" I just say thanks. Welcome, you are home.

Sounds like some a case of needing to placate her beliefs. If it were me, I would get into a discussion about her beliefs without judging them. Lots of 'oh's' and 'uh huh's'...but really listen. That might smash that abutting wall between your belief system and hers. Even if you feel you already know, having her air her belief system might make her inquire more about yours. Discourse can lead to tolerance.

Tell her that if god exists, that it knows exactly what it would take to make you a believer and if it truly loved you and wanted you to believe, it would provide you with whatever it takes.

Just thank her and move on. She (probably) means well. Tell her you appreciate her thoughts. If god wants you back into the flock, he'll guide you there.