First, are you sure your solar wrasse is a female? 2nd, being "fat" and "more aggressive" doesn't suggest "pregnancy", it simply suggests a fish that has settled in well and is getting well fed. Third, without a male around I'd pretty much have to speculate that there definitely won't be any fertile eggs, and probably not eggs at all. FWIW, it is my understanding that wrasses are generally broadcast spawners, simply scattering eggs and sperm and that's that.
Of course, increased aggression could also be a sign that your wrasse is turning from "female" into a dominant male (in the absence of a dominant male).
Sorry to squelch your hopes, but for most fish it takes at least 2 for them to breed. I can't think of very many live-bearing marines (that actually could be "pregnant" at purchase) other than an Adult Shark or perhaps a brotula, or a mouthbrooding fish that's holding a brood of eggs at the time of purchase (although that really isn't "pregnancy" I suppose).
FWIW,
Matt