4me,
First, welcome.
I do know that she says she was ousted because she has children out of wedlock,
The sex itself isn't really the issue, as other posters have noted in the past. It's the most visible reason when pregnancy and childbirth occur. the real reason is attitude. The JW's would call it "repentance;" others would define it as "groveling" enough to earn reinstatement.
As for what to say to her...OK, she's trusted some people too much, or made some bad decisions that got her into this spot--I don't know the circumstances. But their shunning her has the same negative effect that screaming at a child for fifteen minutes over a glass of spilled milk does...shame, hurt, a loss of self-confidence, etc. But the deed is done and now's too late to be yelling about it by others. And most of those wanting to do the yelling are doing it to put on "holier-than-thou" airs anyway.
So, she has children outside wedlock. I'd tell her to love them and raise them to be good people. Curious about the world, wanting to learn, willing to help others, being honest, hard-working, diligent. Tolerant, knowing they will never learn it all. For her, don't wallow in shame or let people make her feel like scum. We all make mistakes. This isn't the end of the world for her. With support from others (not from her family unless she has a very rare breed for JW relatives) she can finish school (if needed), hold down a job, raise her family. It'll be tough but it's do-able.
She's feeling alone, rejected, probably scared, bitter, and will need a lot of emotional support. You can be a big help to her in several areas. You might even tell her about this board. Here she'll find any number of people who can commiserate with her, uplift her, and give her the courage she'll need to face the worst they can throw at her. I'm not suggesting trying to convert her from the JW's to something else...the focus now should be on giving her any emotional help she needs.
Actually I'm assuming she was ousted recently. If it's been a few years then she's probably dealt with many of these obstacles already. But some of the baggage may still be being carried around.
And if you want reasons to get her out of the "faith" this site, and the links at the bottom, are chock-full of reasons why.
Hope this helps.