the recruitment process

No on the Rho gam
Yes it does help the more girls you know, but only if the friendship/acquaintance are friendly. Because it can also hurt you if someone doesn't like you then they can make sure you get cut.
If you have gotten the attention of a house either by rec. friend, attended same HS or you really click with a person who took you around the previous round then you will be paired with someone they will get to know you better to see if you fit in that house and they will do all they can so that you can meet as many people and hopefully you click and make a good connection with everyone you met. All houses do it differently but each house has a system that ranks PNMS that if you keep coming back that helps so you can meet more people. then you might be ranked high, then by pref night you hope you ade it on the first bid list. All that and then hopefully a bid to the house you loved.
Some girls it's an easy process because the house already has "eyes' on certain girls, some girls its work to get to that top of bid list and some girls are lucky and sneak in so that actives are surprise "how did she get in" reaction.

Everything does happen for a reason. Hopefully you go through recruitment again. This year was somewhat hard esp. w/out kappa because girls that would have pledge that house filtered into the rest of the houses. without kappa prob. about 50-60 spots were taken up in other houses, because if there was another top choice maybe so may girls wouldn't have dropped. And even though another house was added it's not a replacement for a top tier.
Also the girls that rushed you could have been disappointed you didn't get asked back to their house. You might have been close but I heard they had a great recruitment this year. There are many professional greek houses that do things socially look into that. Check out zeta they sound like a possibility.
Try not to dwell on it and learn from this and reevaluate yourself ask why it was so important to you to go greek. Maybe we'll see you back next year. Good luck, get involved now there are so many options. Build a great resume for next year. Find recs. Move forward

for clarifications the spots that might have gone kappa I wasn't saying 50-60 spots in each house I meant 50-60 spots spread throughout the 14 houses. I can see the kappa haters already slamming this post.

I respect all houses we all have something great

1) Membership selection is private. You won't know the gritty details until you're initiated.
2) Just because you know a handful of girls in the sorority already, or you had a few great conversations, remember that there are over 130 other voting members. A few people do not determine who gets bids and who doesn't.
3) We are trained to make you feel like you are having a good conversation. Just because you think it went well doesn't mean we're going to highly recommend you to our sisters. Also, we may have liked you as a friend, but don't think you'd get along well within the sorority. It's nothing personal, sorry.

I know people say that grades don't matter after the first round, but they often still do. You might not have been cut but a lower (not low) GPA could move you down on the list. Did you have a rec? In many houses this matters. There are other things chapters rank you on such as did you elaborate on your involvement when you signed up that they can give you more points for that?

If the chapter wasn't interested in you at all, you wouldn't have been invited to Pref. Other girls were just higher on the list because of maybe higher GPAs, legacies and whatever else that chapters uses for Membership Selection. Membership selection within each chapter is private and most members won't share this other than GPA does count. Most actives don't see the bid list so they don't know where you landed on the bid list either.

What can happen is that a chapter has 150 names on their bid list and with a quota of 61, they hit it quota in say the first 70 names (unlikely but an example). So girls who typically get in that chapter who are ranked #102 won't get a big because of how the PNMs above them ranked this chapter.