River Song: Hello, sweetie.
Doctor: Get out.
Donna: Doctor...
Doctor: All of you, turn around, get back in your rocket, and fly away. Tell your grandchildren you can to The Library and lived, they won't believe you.
River: Pop your helmets everyone, we've got breathers.
Annita: How do you know they're not androids?
River: 'cause I've dated androids, they're rubbish.
Strackman: Who is this? You said that we were the only expedition. I paid for exclusives.
River: I lied. I'm always lying. Bound to be others.
Strackman: Evangelista, I want to see the contracts.
River: You came through the north wall, yeah? How much damage?
Doctor: Please just leave. I'm asking you seriously and properly. Hang on. Did you say expedition?
Strackman: My expedition. I funded it.
Doctor: Oh, you're not, are you? Tell me you're not archaeologists?
River: Got a problem with archaeologists?
Doctor: I'm a time traveler, I point and laugh at archaeologists.
River: Ah. Professor River Song, archaeologist.

Once she had herself admit she was a liar, all she said can be taken as a lie.
But I do believe she is a former companion. Maybe even a former lover.