Wolfie is a sweet nickname. Many girls like wolves, not just boys. The meaning itself is gender-neutral -- wolf path. I'd imagine they think it sounds "tough and cool" and likely has some further personal significance we don't know.
I don't expect any of you to agree with me, but I think it's fine. Statistically a lot of this generation's children may not identify with the gender they are assigned at birth anyway.
I just wish we'd see more feminine-associated names on boys.