How do I find in home assistance and transportation for my aunt when she only has Medicaid and Medicare?

Medicaid may be able to provide some in-home assistance. Sometimes this can include cooking. Meals-on-wheels delivers meals in most larger communties. You can find them through a local senior center or social services. Transportation can be sometimes provided by in-home care, as well.
Check with Medicaid and see what they can offer in the line of help. Also, check with your state's version of the National Family Caregiver Support Program, which you can find online on your state's website. Type "aging" in the search box - that should lead you to some links.
Good luck,
Carol