Girls for the most part do develop feelings for a guy through conversation...I have never really felt connected to a guy just through physical connection, but it is always the talking and conversing that has reeled me into liking a guy...

Absolutely it is possible. Often for a girl, a guy's personality is one of his most attractive assets. And the amount of time it takes just depends on the guy and the girl. She may not know the guy is interested if he doesn't act on his liking her in a way like asking her out and it is limited to conversations. But if he persistently pursues her through conversation, he might get up his nerve to suggest a date or a cup of coffee. It is very hard for shy guys. And sometimes they miss opportunities with girls they like because the girl fades away since she thinks he doesn't notice her. Or thinks the guy only likes her platonically...

The reason I'm asking is because my GF wants to flirt with other guys. She doesn't know what guys are out there yet, but will find out when she goes to university. She wants to be with me right now, and I want to suggest just conversations with guys, instead of flirting. Yay or nay?..

You really can't control the situation no matter what you give her the OK to do. You say she wants to flirt with other guys when she goes to University. Did she actually tell you that or are you assuming that is what she wants to do. If she wants to flirt with other guys, well that seems to mean that she doesn't want to be in a relationship with you and wants to have the freedom to date others. ..
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But if she wants to stay in a relationship with you and is in love with you - then you will have to trust her to act accordingly with the new friendships she develops when she goes to college. Being jealous and controlling to her will end up driving her away...

There is no set path to falling in love. I mean, this is kind of like the age-old question of how many licks does it take to get to the center of the tootsie roll pop...
The guy I've always cared the most about, I've never slept with. But we have been friends for MANY MANY years. It really just depends on the person. I'm sorry, but I don't think there's any solid answer like "three, 2-hour dates and she's going to care if you never call her again."..