I think it really really depends upon your interest on her and your usual "teasing/flirting profile". For instance in my case I love to flirt. I flirt all the time even when I'm not interested. Anyway, if you were not interested than your answer was good. You gave her your honest opinion and then threw a little joke in. It was a nice ordinary answer of a confident/funny guy.
On the other side if you're interested this is what I´d say:
HB - So..what do you think?
You - lol...you look terrible!
HB - come on..seriously...
You - I already told you! Awful

.
And thats it. If she still insists you say:
You - Gosh...I never thought one could be so narcissist and at the same time so needy:P. And you don't have to feel bad just cause I hate it:). I am just one opinion in millions!
Seriously, this might seem a bit too strong but in my case it always always works. Of course I say this in a funny/confident way. And people who know me, already know what to expect. When dealing with text messages I always leave some smileys (just like I did in the example) just to let them know you're not being arrogant or stupid. Otherwise they'll think "ok..this guy is telling me this cause he's pissed off with something..maybe he's interested in me." So instead just pluck in some nice smileys for them to feel the ambiguity and irony of speech.
That's it!