She's lucky to have a boyfriend who is so concerned about her safety. Personally, I'd rather have a guy who buys me pepper spray than one who buys me flowers. Very romantic (seriously).
I don't know that area personally, but Bushwick is not the UES or the East Village. You're right to be concerned. And so is she. She will need to adopt a different level of awareness than she would in the predominantly white and wealthy areas of Manhattan.
In addition to carrying pepper spray, I'd suggest that she take a women's self-defense class, designed to teach her self-awareness and effective offense if, god forbid, that becomes necessary. I took one years ago, and it has served me well through many sketchy neighborhoods. (Only had to pull out the offensive tactics once, but use the defensive tactics instinctively everyday.) Such a class would also teach her how to use pepper spray effectively, instead of just antagonistically.
Perhaps a gift certificate to a model mugging class would make a good early Valentine's Day present. ; )
Very un- "sivilized".