She can sing and sing well. Much better than some I could think of.
She is actually a very good signer IMO, she has a great voice when signing standards and sings them seriously.
I was very impressed when she did the Julie Andrews/Sound of Music tribute at the Oscars, much better, way better than I anticipated it would be. And she looked quite beautiful if only she had covered up the tats.
Lady Gaga - Sound of Music (Oscars, 2015) - HQ
And
Lady Gaga - New York, New York (Live From Sinatra 100)
If she doesn't dress in some sort of weird and freaky outfit, doesn't add or delete lyrics or make any political statements while signing it and sings it "straight", she might actually do a good job. We shall see.