She is cute. I have 2 week old kids in with my entire herd. Granted they have a mom but they still get butted and pushed around and then they learn that they can just go under the feeder. I would put them together and see what happens, you might be surprised.
I feed 3 times a day. I take a 1 liter bottle for each kid and let them nurse until they are done. Just like my kittens, I let them refuse the bottle 3 times before I am satisfied that they are full. They never take the entire bottle but I am not walking back to the house to get more so I go prepared. Mine are on a bucket feeder now so they nurse off and on all day and I clean it at night and start over in the morning. A little over a gallon for two of them per day and they are about 4 weeks old.
I would have no problem with the cow's milk. I have raised quite a few that way.
The breeder said that the doeling was eating four times each day but now she's eating three times a day. She actually has no other bottle doelings (my mistake - I thought she said before in another ad that she had two other doelings for sale as bottle babies) but has two that are on their mothers with daily handling. They are for sale separately from their mothers (I guess when they are weaned?). She said they are companions to the black doeling - they live in the same area. She does have the black doeling's brother for sale as a bottle baby though.
I told her what I told y'all about my three month old doeling being the youngest goat kid I have. She said that as long as she won't be alone and is with my three month old she should be fine.
The reason I asked about feeding cows milk is because we have two FF goats in milk right now - still nursing their own kids - and if I milk them both once a day I only get 6 cups total. I didn't think that would be enough. One of my cows just freshened and right about now I can start separating her calf and milking her.