Maybe go for it as a two-step process.
"Kate*, there's something I've been meaning to tell you. I have romantic feelings for both men and women."
And then you and Kate hug and she might even say she knew it all along but no matter what you two will stay pals.
Give it some time, and see what happens. If she keeps trying to set you up with her friends, I would put her romantic interest in you at the low end but certainly her friendship interest would be high.
*Substitute her real name of course. Unless she wants to change her name to Kate.