Nah. Molly killing Bellatrix was kind of a parallel (to a minimal degree) of Lily and Harry. Both of them were mothers who stood up and risked their lives against dark wizards in defense of their children. Plus, I don't think Neville would've कहा "NOT MY DAUGHTER आप BITCH!", which is what made the moment awesome.
Well, I don't think Neville had the दिल to kill someone, even as heartless and cruel as Bellatrix was. There could've been a dueling moment between the two, but all in all I think it was better that Molly Weasley killed her.
In a weird way, both yes and no. Before I read the last book I had been expecting Neville to kill her, I felt he was the character who had the best claim for that right. But I also wasn't really expecting him to be made a killer, in the same way that it fit that Voldemort was killed द्वारा his own curse rebounding and not really द्वारा Harry.
I didn't like the fact that it was Molly who killed Bellatrix, until I read an interview in which JKR explained her reasoning for that choice.