Sounds to me like she's already been De Flores'd

I agree with Lauren. In this passage, De Flores is essentially telling Beatrice that she's now on his level--"You must forget your parentage to me," "made you one with me." However, I feel as though the language here implies that there might be something more at work. It appears as though Beatrice has already, metaphorically speaking, been 'deflowered' -- she's lost her virginity by being an accomplice in the act of murder. As De Flores states "A woman dipped in blood, and talk of modesty?" (III.iv.126). Blood within the context of sex usually indicates a loss of virginity. In this case, Beatrice is 'stained' with blood and has become "one with [De Flores]," indicating, at least in my interpretation, that she's already had sex with him (at least, figuratively speaking). In addition, De Flores says her "peace and innocency" have "turned" on her, indicating a loss of these qualities--two characteristics commonly associated with virgins. The imagery, in this case, seems to allude to the possibility of some sort of sexual interaction on a physical level in the near future.