Well, it's not like the characterization supports any other possibility. This is Selina. If she got pregnant, the only reason she would do anything other than roll by a Planned Parenthood with a check and some spare cash for the taxi is if the kid were Bruce's. No freaking question whatsoever.
Of course Selina giving her up for adoption makes no sense in that case, but it was the ass end of an ass storyline, while "Selina has a kid" in and of itself is not necessarily a bad thing, so I'm more inclined to judge the overarc by the latter concern than the former.