Mean Girls/WMG

Gretchen is a Teen Genius.
Gretchen joins the Cool Asians at the end, and is shown sucking up to them in broken Vietnamese. What does it say about her intelligence that she is capable of learning another language at a conversational level on her own, in high school, as a social activity?

This may also explain some of her disillusionment with the Plastics, and in turn, why she was targeted by Cady, Janis and Damian to break up the clique -- she might have been upset with having to hang around with people like Karen and Regina in order to be popular. And not for nothing, but she was the only brunette in the group.
 * Apparently that "Vietnamese" she was speaking was really just jibberish.

Janis ruined everything.
If one stops to think about it if Janis had never even placed inside Cady's head the idea of posing as a Plastic mainly/solely as a part of Janis's revenge scheme on Regina or (going further) if Cady had never met Janis (and through Janis) or Regina, Cady's entry into the American teen social ladder might have occurred much differently.

As was stated by Damien at the start of the film Cady was a "Hot Little slice" that could easily become integrated into mainstream High School life that after only a small "Refinement" and update in her personal fashion sense, Cady would have been easily considered as or more attractive then any of the Plastics.

Also Cady herself states that she was only acting "Bitchy" because she had to pose as this to fit in with a clique of other teen "bitches" as part of Janis's (and in part Cady's own) Revenge scheme and because of this Cady was unintentionally Becoming the Mask. Also it can be argued that Cady only acted in that way simply because she was totally unacquainted with a more "realistic" American teenager social structure and simply assumed that all popular girls acted in this way or manner.

Finally Cady intentionally "Dumbed herself down" (although this was only to get closer to Reginas Ex not for revenge so YMMV on that one) degrading her persona (and grades) further.

So simply put by the previously stated points without Janis's influence Cady could have still become the most popular girl in school by her own beauty, intelligence, and general kindness that she might have discovered or learned on her own and by others, and would have dethroned Regina as Queen Bee and taken over the plastics without destroying her own personal sense of character and/or reputation and morality.

Now technically one can argue that Cady's moral and character decent was the entire point of the film It can be essentially said that Janis by her own childish need for "7th Grade" Revenge ruins the chances of this alternate scenario ever happening (including becoming one of the clique herself and a better friend of Cady later on).

However in fairness to this it genuinely does appear that near the films end that Janis does realize what directly she had done to Cady and tries to make amends (in a small way), although she may never have realized exactly how much she destroyed as she unwittingly lost the possibility of future popularity, friends, and increased happiness not just her but the entire school Might have gained in the process. Instead of the reconstruction from the social ruins that are shown at the end of the film.


 * It really is an interesting thought experiment to imagine how the plot would have played out if you take Janis out of the picture. Regina still notices Cady and invites her into the Plastics, and Cady jumps at the offer (remember, she was desperate to have friends, and even with Janis's opinion in mind she still thought Regina was sweet). Since she isn't reporting to Janis, she spends a lot more time with the Plastics (and isn't wary of their motives), so pretty soon she completely identifies with their values -- enough so that, after Regina steals Aaron at the Halloween party, she actually believes the "explanation" Gretchen gives her. Cady goes on to become Regina's second-in-command, while still dumbing herself down to get Aaron to tutor her. Grethen eventually cracks (even without the candy cane sabotage it was obviously just a matter of time) and reveals Regina's infidelity to Cady. Since Cady by this time is probably quite the schemer herself, she uses this to make them break up. Regina stays with Shane and Cady eventually gets together with Aaron (since Regina is still Queen Bee, Cady isn't pressured into throwing her party, and thus doesn't make her drunken confession to Aaron). Cady is nominated for Spring Fling Queen and wins, with Shane as King; Regina is definitely not okay with this. This much I can base on the plot of the movie -- how it goes on from there is much more speculative.