Is it normal for me to have these thoughts about my wife?

Just because the friend is like that, doesn't mean your wife is. I understand, though, but you can't drive yourself crazy thinking about it or things that never happened. If she gives you reason, like talking about going to different places or the friend meeting a guy (which also means he had friends with him who were chatting up the other women), or anything out of the ordinary, yes, ask her about it and don't pull any punches. Get honesty.

I have an on-again, off-again gf who is the most beautiful woman I've ever known or been with. Guys just..Go to her when we're out together or even when she's at the drugstore, etc, by herself. Men go right to her. I've had her at the sports bar I go to several times, and know to not leave her side for long if at all. One, she's also a natural flirt and sees the guys attention as "being friendly" and reminds me that I'm the one she's going home with. And two, even some guys I know from the bar will come right over, plop themselves down if a seat, of course, next to her, is open, and chime in. She's a nice person, so, will let them in our conversation or start her own, until my patience is gone.

I know nothing goes on with these other guys, but do get your point, and is why I'm advising you to not drive yourself crazy thinking or worrying about it. Just ask her.

If she were lying she’d probably have some pretty obvious verbal and non verbal indications.

Somewhat normal, but you need to trust your spouse.

A reality is that you really have no way of knowing. I'm aware of only 1 indication that is usually right in regards to a hidden affair. If a partner says they need their own apartment so they can have their own space... It's usually because they need a place to have sex with someone regularly that cheaper than a hotel. The key exception is that highly creative people may need their own space just to be creative.

Absent the request (or setting up) a separate apartment there are no reliable signs unless you catch them.

I also agree with others that many people are a bit flirty with others and have other opposite sex interactions and never cheat at all.

My one suggestion to help your situation is to read "The 5 Love Languages." If your wife is "stepping out" there is a reason...and something may be missing in your relationship (and you currently have no idea). That book will most likely allow you to identify any missing item and correct it, and invigorate your marriage in the process.

I wish you well with this,

Well she's probably not going out anytime soon at least. Just have to watch her actions. Be evasive with the phone or having to go out at certain odd times. Hopefully you're just being paranoid