You are and have done everything that I with all my experience and knowledge of LS would be doing.
I'd like to offer you some more info.
Children's Vanilla Pedisure is ok to give in small amounts via syringe if she is not eating.
Watermelon is good to give in small pieces, you can drizzle the lactulose ontop.
A few apple bits (no skin) and romaine lettuce are good treats.
I prefer: Hepatosupport and Vetri DMG from
HomeVetŠ Natural Pet Care
These are easier to give then denamarin (which I believe has to be given whole and on an empty stomach).
Baking the L/D may be a nice treat for her
You can coat the RC kibble with a very little, tiny bit of low sodium goat cheese or Friendship Brand No Sodium added 1% cottage cheese.