「お休みなさい」と「お休みなさいませ」は意味が同じですか。
The other day,I was chatting with someone on Skype,when I suddenly felt sleepy.So I said "Oh,sorry,I feel very sleepy,maybe it is because I've drunk too much at lunch.And that was the reply I then received.

Question

Answer

Both would be used same situation; as you said "I'm sleepy" above.

Then a  friend , a husband or your colleague says to you お休みなさい。

However you as a good old japanese wife, a servant girl, a Hotel stuff or someone ranked lower than adressee in Japanese culture might say お休みなさいませ　to an addressee.