If someone buys you a present, do they have a right to take it back if something happens?

My sister and my cousin recently bought me a laptop for my birthday. i was really excited for the gift when I got it and I loved it. Recently, My sisters changed alot and yells at me, is rude to me, is bossy, threatens me alot etc. etc. Alot of the time, she uses the laptop as leverage to pull me in her direction and kind of use me as a puppet. She asks me to do something, and If I say no, she'll throw it in my face that the laptop was really expensive. If I still won't do what she says, she tells me she'll take away my laptop because she paid for it, even though it was a gift. She didn't even pay for all of it. Don't get me wrong, I appreciate the gift and I love her for getting me it, but I cant take her personality anymore. Most of the time, I do what she asks me to because she's really good to me, but she's changed alot and really pushy and gets mad for alot of stupid things. I pretty much do everything for her and my other sister without question, even if sometimes i'm tired. The way she treats me (I personally think) is ridiculous. Whenever she's home, she makes me get off my computer, in my room and locks the door. Even if I need something from my room she won't let me in. She also always throws in my face that she buys me stuff all the time like clothes and video games. But she honestly hasn't bought me a single thing in a year, and all she buys me is food, and i'm overweight which doesn't help me out. I'm not trying to be selfish here, saying that she has to buy me stuff, I don't even ask her to buy me stuff, she offers. I'm just saying don't throw that in my face when all you buy me is food and yell at me for being fat. But my main question is, she bought me a laptop for my birthday, does she have the right to take it away even though it was a gift?