I give as much hay as my girls want. When I was on a tight budget I gave them 1 flake each, morning and night, which seems to be a base for maintenance. Though I find they will eat a bit more than that and do a bit better if they have it free choice.
Re grain my four does plus 1 kid get the following, twice a day. The scoop I use is a breakfast cereal bowl.
6 scoops 'shandy' chaff (shandy chaff is wheaten chaff, oaten chaff and lucerne chaff mixed together)
2 scoops cattle mueslie
1 scoop whole lupins
Then when they are on the milk stand they get 1 to 2 scoops of cattle mueslie extra (depends on how quick they eat and how slow I milk
, and also how heavy a milker they are)
So you can see I mainly feed roughage, but I would say a MINIMUM of 2 breakfast cereal bowls of a good grain if she is milking, but if a heavy milker I would prefer more. A dry doe probably only needs 1 or 2 plus good roughage and/or forage