I've liked this ever since being cast as Petronella Van Damme in an 8th-grade production of The Diary of Anne Frank (the only time I've ever heard it, honestly)... even if it does seem like a portmanteau of "petroleum" and "citronella." XD It's still an attractive, strong, elegant name.
This name is alright, really, when I think about it, but it does sound a bit overly-feminine, and just a bit flouncy, but Nella is an ok nickname. I suppose. :)