I take 2hrs off the upcoming invoice. But it's a one-time deal per instance. I too don't like the tone your client seems to have - but then I'm not in a good mood at the moment so maybe I'm being too sensitive. LOL

Why would you give someone a referral reward up front, or a reoccurring one too?
I really find her request rather bold, but if you're comfortable with it, then I guess go for it. However, if it were me, I would just thank her for the referrals, & tell her "this is my referral policy" - take it or leave it. lol