I agree with Raptureready...a trip to the vet is in order. Frequent peeing is usually a sign of a simple bladder infection, cheap and easy to treat. Her confusion may be because she keeps having to pee or is suffering discomfort. I have a beautiful old girl..Sarah who is very similar to your Minnie also 16...Sarah had a bladder infection about 5 yrs ago, she never messed the floors but was using the shower drain, which she only does if desperate/accidently locked inside.
Senility is common in older cats, my sister has a cat who is 19 and has been diagnosed with senility...she has become very vocal and wanders about at night...
Hope all goes well...keep us posted.