…し means that the clause with it is a part of reason for the main clause, in other words, 彼女は優しいし、綺麗だし、楽しいし。だから大好きだ implies that you might love him/her for other reasons than being kind, pretty and fun.
Incidentally, 飲んだしよ is not accepted in Standard Japanese, it sounds fairly rude (in its realm). よ is accepted in Standard Japanese only when it stands for a vocative case (dated expression) or a sentence ending particle. Other usages are considered a slang (including so called feminine language). Sentence ending particles need to follow either a terminal form of verbs (or adjectives) or another sentence ending particle. Since …し is basically a conjunctive particle, the form of 飲んだしよ is not a main clause with a sentence ender but a sub clause with a filler (or interjectional particle or whatever).