How to Discipline Her??

My neighbor spends a lot of time at my house. She's practically a sister to me. I spend a lot of time watching her daughter, now 4, who I've known since she was less than a year old. Lately she's developed a really nasty attitude, and when I have to send her to time out, I explain to her why she's there and what she should have done instead. The past three times she's been over, she rolls her eyes at me during this conversation. A very long, drawn out, dramatic eye roll that she learned from the girl her mom babysits. I've explained it's rude and unacceptable, so she knows, but she doesn't care. She did it twice yesterday. I told her mom about it and she said they've been having issues with that at home too, and to just spank her when she does it. But I don't really agree with spanking. I'm not comfortable doing that to a kid. There has to be some other punishment. She's already in timeout, and if I tell her she has to stay longer because of that she just says "Fine! Then I will!" Taking away toys doesn't faze her at all. What can I do!?! She's here today and I'm sure it will be an issue again because she's done it several times every time I see her. I tried explaining that it hurt my feelings when she did it. Her response was another eye roll