i think her body will yearn for more big black cock once she'd had one, but also her mind may refocus. my exGF for example was so well fucked by her first black man that she began to think about sex with him or other black men more and more.
The more she thought about them for her sex the less she thought about me. i was basically a pityfuck to begin with for her, so it didn't take long until she not only cut me off but also took away my erections and then she totally focused on real men for her pleasure.
So my advice is don't worry about competing with him sexually, as you had mentioned, since you won't be able to.