I mean is she thinking that since the guy is in "the world" that, no matter how nice he has been, he must be inspired by satan or something?
Not exactly, but he is considered "worldly", and that's not a good thing. JWs are discouraged from forming friendships outside the organization, and that goes double for romantic relationships. They do believe that Satan is always trying to mislead them, so she might see it as Satan tempting her.
Has she likely consulted w/JW family members or JW friends who negatively influence her?
It's very possible, or she might have kept the relationship secret, it's not something she could be open about.
Or, have her "brainwashed" beliefs just short-circuited her ability to think rationally?
Yes.
Does she likely experience "mixed emotions"?
Yes. There are more women than men in the organization, it makes it hard for women to find a suitable partner. She is probably quite attracted to you, but at the same time to marry outside the religion is socially unacceptable. They also are quite strict about sex outside of marriage, so that can create a lot of guilt, if that has happened between you, or if she has even thought about it.
It's hard for a non cult member to get how much they manipulate their members. It is a religion of guilt. They disfellowship and shun people, for things most people consider normal. They use guilt, fear and obligation to keep people in line. She might sleep with you in a moment of weakness, then feel guilty and confess to the elders. This might lead to being privately counseled, what they call "reproof", or public reproof, or disfellowshiping, it depends on the elders. If disfellowshiped, her family and friends would shun her, it might be months, if not years before she would be allowed back. It's not a good thing to go through.
I wish I could be more hopeful, but this is how it is. We have had a lot of people come here with similar stories, it doesn't usually end well, the deck is stacked against you.