Is it normal to lust over an ugly girl?

There is this Young Girl that started working where I work and to say the least, she is quite Homely and Shy. She wears Clothes that aren't very Revealing or Flattering either. Her Shyness is what has really drawn me in to her.
Because in a way, i feel some sort of Sympathy for her at this Point. By nature, i am the kind of guy that has Empathy for all people. In Sarah's case, my Empathy is Two Fold. She has caught me looking at her many times and she always turns away when she does see me looking at her. I look at her because in my mind, I kind of pity her. I am trying to find some kind of beauty in her. Well Low and Behold, the other day, she wore a pair of Tight, Revealing Jean's and a Tight Shirt that were actually very Flattering and Complimentary to a body that I never knew Existed. What I saw was an Ass that was to die for and a pair of really Hot Tits. So now, as you can imagine, I am really checking her out and Lusting over her. Again she caught me looking, but this Time it was in an Admiring way. Being an man with an Ass Fetish, you can imagine how I was feeling. I had to walk off to the Bathroom to Jerkoff as I was overwhelmed with the Situation and what I saw. The next day she came in with another pair of Tight Jean's that looked better than the ones she had on the day before. This time she replaced her Glasses with Contacts, which made a Major Improvement in her Face as a Whole. It was Odd because when I would try and sneak a glance at her, she was actually staring me down like she wanted me to know I was looking at her. As it stands now, I am Lusting over this Ugly Duckling and I really feel the need to get in her Pants. How am I going to Accomplish this and be Discreet at the same time? I really want this Girl in a Bad Way.