You have to understand that asking her to consider dating you would be a major complication (to say the least) to her friendship with your ex.
I think you should ask a warm, sensitive, posek, someone who deeply understands peoples feelings to guide you on the proper steps to take so as not to mess it up, and ease the burden of hurt all around.
In my limited knowledge, i’d have someone “let it slip” to this girl that she was mentioned as a shidduch to you a few times and you were very open to it, but didn’t want to put her in a tough place by making her decide.
However, is she was open to it, then you’d be very happy to give it a go.
Don’t let her know you sent someone, it should just be a scoop that someone close to you let slip.