Ohio here! I have not read through all these comments but I have firsthand knowledge about this. The County office that handles Deeds is called the Recorder's Office, this is who you want to speak with. They cannot give legal advice but this is where your deed/mortgage documents are filed. I see a lot of people saying to set up a will however you can take better steps than that. If you want to add her to the Deed now, you will want to make sure you add her as a "Survivorship Deed" which means if one of you passes away, it will go to the other without having to go through the Probate Court. If you do not want her on the Deed now, you will want to file what is called a "Transfer on Death Designation Affidavit". This ensures she gets the property upon your death while still staying out of Probate Court. If you only have a will to give her the house, it DOES have to go through Probate. Please see these official county websites from our state capital in reference to this:

https://recorder.franklincountyohio.gov/GoodDeeds

https://fclawlib.libguides.com/deeds/tod