My sister wants me to claim her in my taxes, and to give her the refund she got and I was wondering if that would affect my refund?

Other answer:

The real problem with the idea is that if the IRS decides that you weren't entitled to claim her (whether you can claim her is up to the government of the United States of America; it is not up to her), then you will have to pay back the refund. She probably won't give you back the money, so you will have to use your own money to pay back the government.
Pascal the Gambler:
You owe her nothing if you claim her, and you can only claim her if she qualifies as your dependent.
dont do it! it will just get you into trouble with the irs!
Unless you can legally claim her, YOU can get in serious trouble for this scheme. And if you can legally, then you don't owe her any of the money.
Mark T:
She wont get a refund. , you will..
It is a bad idea to file a fraudulent IRS tax return just to benefit someone else .
That is Federal crime and the IRS can audit you anytime in the next 7 years
something they do randomly or if their system flags your return for an audit.

Also, the less taxes you pay , it will affect the amount of monthly Social Security benefits you
be entitled to when you start collecting SS . It is based on how much tax you have paid
during your working years. The less fed taxes you have paid, the lower your monthly SS benefit will be.

Also, i will guess that she is someone that is already scamming the system getting welfare benefits etc.
Now she wants to use you too , right ?

What you said makes no sense. If your sister is doing your taxes, why would "she" get the refund? And who is the "her" "she" is going to give it to?