Of course those texts were a threat. He told this woman that his posse was coming to dig up dirt on her. That's threatening.
"a statement of an intention to inflict pain, injury, damage, or other hostile action on someone in retribution for something done or not done"
Brown essentially said:
you shared your story about my actions > I don't like that you did so, and I think you did so because of 'x' > my friends are going to dig up crap on you to demonstrate you're flawed, and therefore take the pressure off of me.
Maybe not a physical/violent threat, but certainly a threat nonetheless.
And the ironic thing is that the woman he texted *never* filed criminal charges or pursued a civil suit, she only shared a story of her experience with Brown with a journalist.