Are you still milking her or have you given up? If yes she would need a bit of some kind of concentrate - have you tried Alfa A and/or readigrass? Access to willow branches, ivy, bramble? Offer fruit/vegetables like banana, carrots, swedes, cabbages (the outer leaves of cauliflower is one thing mine really love or kale)....
Soaked warm sugar beet shreds - maybe with a drizzle of olive oil on it?
These are things that I have tried more or less successfully.
No chance shhe has been with the billy? Cloudbursting?
Can't otherwise think what may be wrong with her if everything else (incl droppings) are normal.