I think the "leverage-for-forcing-a-trade" hypothesis (i.e., Angel as Manny Ramirez redux) is more plausible than some deep psychological explanation. Although, if she is a free agent after this year, and since Atlanta clearly has a good shot to do well in the playoffs this year and possibly even get to the finals, you would think she could wait until after the season to make her exit rather than risk being traded to Tulsa or Washington (for example).
I am trying to think who the Sun might offer for her if that is the case. Certainly they would give up a #1 draft choice (maybe even 2 years of them), but I think other teams would offer current players. I don't think that the Sun would or should give up Tina or Asjha or Kara to obtain Angel. Maybe Renee, Misty Mims, and a #1 draft choice -- but that hardly seems like sufficient compensation for Angel, if her head is in the right place and she really wants to play for the Sun. I'm sure that any trade would be conditional on Angel signing a contract that extends beyond this season.