Well. Should help her breast envy complex a bit, at least (yes, she totally has one, there are moments).
That aside, well done. It's a nicely drawn picture; I'm no art major, so I can't offer a good critique, but it's a nice drawing anyway.
As for my guess at the father... eesh. Tough call. Wendy's not really shipped in-universe with anyone, is she?
I'd actually almost be willing to suggest Mirajane as an out-of-nowhere crack pairing, depending on how, uh. Thorough her transformation magic is. Is it an illusion or actual bodily alteration? Not the Satan Soul stuff, but the random transformative things she uses now and then. Mostly had Mirajane come to mind because of her odd little motherly/sadistic dualism.
pretty good, I like it, thought she looks 13 or may 14 there?...anyway though I am not sure it would be within her character to suddenly sleep with one of her fairy tail members; unless it happened in the fourth ova when she got drunk XP. Ether way, it makes me ask, who's the father?