Do not just plead guilty. This will result in a permanent criminal record. You are likely eligible for a deal to avoid the conviction. Hire an attorney or use the court appointed attorney for sure.
It is very important to plead Not Guilty and either ask for a Court Appointed Lawyer if you cannot afford one or seek an attorney of your choice. Domestic Violence charges do leave a permanent record. Further, it is important to know that once police are called to the scene of the incident or a police report is made (many times both occur), the case is now out of the complaining witnesses hands or your hands and now up to the local prosecuting agency to pursue charges. If your local prosecutor believes a crime was committed, then they will prosecute the case despite whether or not an individual does not want to press charges. However, the mere fact that your sister is not seeking charges may give you and your attorney lots to work with in finding a good resolution, perhaps a dismissal. if no dismissal, The domestic violence statute in Michigan also has a voluntary probation section that will allow you, if you successfully complete a term of probation with conditions, to go forward without a crime on your record. Finally, it is important to select a skilled attorney with trial skills if you believe you are innocent and no acceptable deal can be negotiated.
This comment provides general information and is not meant to be legal advice as there are many facts that are not considered in your question nor is there a way to fully explore your case in detail without more facts. Please consult at attorney for legal advice suitable for your individual facts. My response does NOT mean we have established an attorney- client relationship.
When you go to the first hearing, the court will do to things: First, arraign you (if they haven't already) and set a bond. This is a portion is important so that the bond isn't too difficult for you to comply with. Second, they will ask whether you want to plead guilty, not guilty or stand mute to the charges. If you plead guilty, you won't have an opportunity to defend yourself and it will go on your record. There are several possibilities that can occur which would allow you to have no permanent record. They will set the matter for a pretrial and ask you if you want a court appointed attorney. If you get one and decide later to retain, you can always do that so if you don't have money right away, be sure to ask for a court appointed attorney.
Once a complaint of dv is made, the prosecutor decides whether or not to proceed with charges, not your sister. However, her reluctance to go forth with charges will make their case much more difficult and your case much stronger. Good luck.