I need some advice... really...

Ask you all huh.. and you must reply! Esp if you've been reading my blog. Your friend here is in need of advice.

As you all know, I am a worry wart... and I tend to overcomplicate, overthink and essentially hyperventilate on things that are rather miniscule to others.

My lady boss, her being the one who

1) Hired me;

2) Appraises me; and

3) Whom I have to work for and with...

seems to always be making snide remarks, most of which I just smile/laugh off... but the truth is, being the defensive person that I am, I actually want to explain or rebutt her comments. Which I do sometimes, then she will have a look of irritation on her face. For eg., just so you have a feel of her personality, and my stupidity

Scenario One
Walks past me while I am waiting for colleague for lunch.

Boss: Hey, wanna lunch?
Me: Oh, I am waiting for XX.
Boss: Hey, you need to wear higher heels. Your pants are too long.
Me: Haha.. no way, I can't balance in them.
Boss: Then you have to tailor it.
Me: Already tailored. Besides I like them slightly longer and to wear them at the hips, it's more "in".
Boss gives me look of exasperation.

Scenario Two
Standing around, some celebration of colleague's bday.
Boss: (looking at colleague X) You people seem to like to have your pants too long these days.
Me: Yah, it's a bit more fashionable, plus, your pants doesn't ride up when you cross your leg.
Boss gives me look of exasperation.

Subsequently, informed by colleague X that both herself and I have been signed up for grooming lessons. (-.-||)

Scenario Three
This is a meeting with a consultant, and I have no idea why, but we started discussing the Masters course that I am taking.
Consultant: Oh, by the time we're done with the project here, you can use that as your dissertation.
Me: Haha, that's ok, I have opted for the coursework route.
Consultant: Oh ok...
Boss: Sorry, I don't understand. What do you mean coursework?
Me: Oh, it simply means that I take more modules instead of doing a final dissertation to graduate from the course. It's easier, and requires less committment from me.
Boss: Oh, my rating of you has just gone down. (I swear, she said exactly that...)
Me: Haha...

Now... I need your advice. What I really wanted to say at that point of time was, "I opted for that because between work and school, I have chosen to focus more on work, cuz obviously, you guys are the ones paying me." But, then I cannot possibly say that, not when the consultant was there... and even if the consultant wasn't there, I have to learn to stop rebutting my boss.

Right or wrong decision? What would you advice me to have done?