You can rush through act 3. Just do the quests you find "fun" and leave the rest. You need to do the Orin path and go through all the Bhaal fights to reach her, these can't be skipped, but most others are optional, imo.
E.g. when you make a deal with Gortash and stay true to it, you can avoid his boss fight, the foundry and the submarine fights. You will go together to face the netherbrain after you took Orin's stone, and mr. brain will zap Gortash for you , whereafter mr. squid will open the portal for your party and the 3 stones, and you can go to the endgame, and have your first real chat with Minthara after that.
