What does lady friend mean?

Found out this guy who I’ve been causally seeing was messaging another women and going to dinner with her. I asked him about it and he said there was nothing romantic going on. She didn’t want a relationship. He told me he hasn’t heard from his lady friend in a while. Actually asked me if I had messaged her. If that’s why he hasn’t heard from her. I told him no. His response was I wouldn’t blame you if you did. You would have every right to do that. Though she would of told you the same thing that there’s nothing romantic and they are just friends.
What does lady friend mean?
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