If I opened an checking account and put my sister on my account as a user. And she gets a court ordered garshment can they come after my checking account?

Yes.

They will freeze the account, and it will be up to you to prove who's money is who's, and could tie the account up for months before you can get it straightend out.

Yes any account that has her name on it will be subject to being attached. Your best bet is to go solo on your accounts because as stated above it will be up to you to prove what money is yours and it could take days to straighten out

Absolutely.

If she's an authorized signer on the account, it no longer is solely held by you but "jointly" held by both of you.