I'm loathe to categorise Trish as a diva. When I think about divas (which is quite often, lol) I think of the generally talentless but nonetheless good looking and (sometimes) good on the mike ladies. Trish has transcended that level due to her wrestling ability, and due to her ability to carry a feud (look at what she's done for Viscera and Christie Hemme. Imagine what she could do with talent to work with).
Workers like Trish, Lita, Chyna (back in the day), and Gail Kim are above the 'diva' title. Trish, in particular, is better than some of the WWE's midcard at the moment.
That being said, my favourite 'diva' would have to be Stacy.