If you go to the Liver-Flush forum and search on breastfeeding and LF, you'll get information saying Liver Flushing is OK, and you'll get info saying it's not. I can tell you a few things about my experience/offer some ideas --
-- I did some Liver Flushing with Ann and Merry were 18-19 months old and they seemed no worse for the wear. I was still nursing them, I think like you at night (or maybe in the early morning and the night).
-- It is hard to do the Liver Flush and need to be near the bathroom that whole morning when you have two toddlers who need attention!
-- Your daughter has a pretty clean system and her liver is probably better equipped to deal with toxins than yours.
-- Ultimately you wil all be better off if you get your stuff out. Breast milk is a very protected system with lots of filters, so to speak. I think the hepatic system is, too.
I remember asking about this at Liver-Flush and someone was really sort of nasty to me, a la, "How could you THINK of exposing your children to all these TOXINS???" and I was like, Whoa -- I am not making a rash, harsh, selfish decidion here!
You'll be OK, in my opinion -- others may disagree, but I've got two healthy daughters still.
None of this stuff ever turns out to be as harmful as we think it might. I remember being really sared of oil pulling before I did it. Me, who has never thought twice about putting a lot of crap in my body!