There are film clips out there from past years where Trump is stating how pro-choice he is. Dies she really believe he had some conversion on this at the same time he decided to run in the GOP primary??

She'll cling desperately to any rational she can find, no matter how unreliable and untrustworthy Trump is. Clinton will definitely do her best to appoint Roe v. Wade supporting justices, so that makes her the Ultimate Evil.

I have an older brother who is the same way. Tries to irritate me by saying that he is voting Trump because their isn't someone more racist on the ballot.

My sister is actually very smart. Unfortunately she uses the power of her mind to construct whatever elaborate rationale she needs to believe whatever she wants to believe, do whatever she wants to do.

She's say it doesn't matter what he's done in the past. Even if she doesn't fully trust Trump to appoint anti-abortion Justices, she does fully trust Clinton to appoint pro-choices Justices, so Trump wins in her mind.

There is no way that Trump is even remotely "pro-life". No one in his circle would ever have to worry about abortion. If one of Trump's wives or daughters or close friends needed an abortion, she would have plenty of money to have it done anywhere she wanted. The issue literally wouldn't affect anyone in his world. He is just playing people like your sister, but unfortunately she'll buy his schtick as they always do. Just like the fact that Trump is about as far away from evangelical Christianity as you can get. I bet the man can't name two books in the Bible and probably can't quote a single verse. How is he now held up as some paragon of family values? I can't comprehend the mind-twisting necessary for these people to support him.

...about abortion because...

(1) It's a tribal signifier for fundies and conservatives.
(2) It's a "purity" thing.
(3) It gives them a cheap and easy way to cast themselves as the people who "truly" care -- they get to be self righteous simply by imposing rules on other people, not having to do any hard work themselves, not having to care for people after they're born, not having to worry about innocent lives lost to war or gun culture, etc.

Republican Jesus don't care.