The real question is - what is the neighbor's expectation around cost of repair? Full fender replacement or a quick patch and paint job? And if fender replacement, OEM or aftermarket? If it were my vehicle, I'd want it restored to original condition and if it didn't have body filler, it wouldn't when repaired..... the neighbor is offering to pay for repair to avoid insurance issues and possible increased premiums. Body filler shouldnot even be a matter of consideration. Should the OP try to sell or trade the repair will show up and diminish the value.