bombshell dropped....need advice!

I've just been informed my husband of 5 yrs. came home from work early in the summer of '07 and caught my then-16 yr. old daughter (from my previous marriage) in bed with her boyfriend. My husband told me she (& the young male) begged, cried & pleaded for him not to tell me and they "would never do it again" so he didn't tell me. Then he catches them approx. 3 wks. later, same cenario. He bargained with her and told her if she started treating he & I with respect he would keep up his end of the deal. So he still doesn't tell me....until last night. She was disrepectful to the both of us for the last time and he told me what transpired back in '07, in her presence.

I don't know who I am madder at.....him for not telling me then, so we could have punished/disciplined her then or her for what she got caught doing! So how do I punish her now........? And forgive him for not telling me sooner? Help....I am really struggling with this.