I told my former T that I love her, in a roundabout way. She said it's not unusual for clients to love their Ts.
I told my current T that the child parts love her. She said something nice, but I don't remember what. I hemmed and hawed about telling her the adult me loves her too. But then I asked her in a negative way, "you can't tell me you love me?" and she said that wouldn't be genuine, but she cared about me an awful lot and I was very special to her.
She did say "I love HER" once, referring to the child part when I directly said that part wants her to say she loved her.
So, I guess this is a warning that it's okay to tell your T that you love her or him, but don't expect an "I love you" in return.