Quantifier + comparative - so much drunk or so much drunker

I'd like to know what´s wrong in the sentence:

I didn't drink any more than the guys did, but I got so much drunker.

I believe it's the quantifier + the comparative that is wrong, but I'm not sure why. And one more thing: it's a teenage girl talking about hanging out with friends: when she says "guys", is she referring just to the boys in the group, or to the group in general (boys and girls)? Thank you!

It isn't technically grammatically incorrect, but it is a little bit of an unusual way of phrasing it, which is probably why it sounds just a little 'off'. I believe the more common way to phrase it would be:

I got so much more drunk.

Again, though, it is still a proper way to say it. It's just not as common.

There are some cases where this type of phrasing would not be correct, as in the following example: "I think my friend is more beautiful than me." Here, one could not substitute "more beautiful" with "beautifuller", as this is not a word.

To address your second question: In this particular sentence, it seems she is referring to her male friends. An example of a gender neutral use of the term "guys" would be: "Hey, you guys! Come over here!"