My mom moved in with me. What will happen when I have to apply for Medicaid when her money is gone?

If your mother is in a nursing home they started her Medicaid application the day she got there. In fact, it may have even been started from back when she was in the nursing home for rehab 2 1/2 years ago. Nursing homes don't waste any time waiting for a person's assets to be spent down. They get after Medicaid straight away. You will not have to do her Medicaid application if she's in a nursing home.
Ask the nursing home who your mother's Medicaid caseworker is because she has one. Get a name. If they don't give you one then call your state's Department of Social Services and talk to someone there. They will be able to put you in touch with this person. They are the one you should be communicating with and who you can explain your situation to. Don't try to with the nursing home. All they're concerned with is her house being sold immediately and the proceeds being handed over to them at once.
Find out who her Medicaid caseworker is and deal with them. They will be more reasonable to you than the business office of a nursing home.

The app will require info like her SSN, recent banking statements (like within 3 months of the app date), list of some other assets that she owns, like house and car, marital status, medical bills, etc. You do not need to be her PoA or guardian in order to complete and submit the app for her. FYI if you get a letter back from Medicaid open it immediately as they are probably requesting more "proofs" (their word) and you need to get the info back to them within the week or you may have to start the app process all over again. I learned this the hard way :-(

Check with the nursing home business manager and ask if they can help walk you through the Medicaid application process. This was a huge help for us. My mother stayed in the same place from using a long term care policy, to private pay, to Medicaid. Get started now, it takes a bit to process the application