I agree to see if the milk replacer is the same type she was using. If they had other cattle and you don't she may also be lonely and changing her whole life/routine can make a difference.
I would also try her milk in the bucket as opposed to a bottle. Also, try some probiotic paste or boluses to get her gut tract working a bit more so she might be more hungry....like when your stomach growls.... Vit B shot will also help stimulate her appetite.
She should be getting 2 qts twice a day so if you have to force feed her then I would. Make sure whatever milk replacer you are using is ALL MILK milk replacer and not SOY based. It will say right on the label Most are 20/20, fat /protein and will say all milk protein. They will do poorly on soy based and they don't like the taste of it as much unless they are real hungry. Make sure it is warm, not hot when you put it in the bucket or the bottle.
Seems to me that the lady did not tell you straight if she said she was drinking good from the bottle. Most will do fine and then might feel the separation etc a day or two later, but to just not want a bottle from the start is suspect as to how well she was doing before.