What you're asking is "how do I deal with a woman who is hung up about her ex?" -- but what you're really asking is "how do I date a woman whose ex boyfriend is more attractive than I am?"
If she's hung up, you deal with her at arm's length like any other emotionally unavailable woman. If you believe yourself to be an inferior option for her, that's your hang up, not hers.
"Alpha widow" is a made-up Rich Cooper red pill term. All attractive women have been with "alphas" and "betas" within various social contexts and have left one for the other, or maybe vacillated back and forth between the two over the course of their lives.
This weekend I saw a young couple, maybe late teens or early 20's, passionately making out with each other on a park bench. The girl was a 8+. The guy was a 5'7 scrawny guy who was very well-dressed and looked to have an expensive haircut. Not someone who fits the definition of "Chad." Clearly, this kid has high status in their social sphere, which he enhances by carrying himself in a high-value way.
If he dumped his hot girlfriend, I doubt we'd refer to her as "alpha widowed" and unattainable by anyone else.