In my experience, which some may relate to, I usually develop onenitis for a woman because of one or more of the following reasons:
1: a Blue Pill idea of love
2: a conscious or unconscious desire to fill a void in my life
3: lack of options
Which in turn cause me to pedestalize the woman and create an idealized version of her in my mind that I obsess over.
Usually while I'm in that obsession I'm too emotionally compromised to actually work through my onenitis with that particular woman. In other words, I consider any further dealings with her as detrimental, as the obsession will cause me to ignore or minimize her red flags.
In terms of a solution, in my opinion, I'd rather detach at that point from the object of my onenitis (go no contact with the chick I'm obsessing over) in order to give myself the time, space, & perspective needed to identify the cause of it...
As I mentioned, it's usually one of the 3 reasons I listed above. In my case, it's usually reason #2 or #3 (which are often tied together). #2 because I'm off my purpose & have no goals I'm working towards, and #3 because I am desperate at that point in time and get attached to the first girl I can. A solution for me in those scenarios in a nutshell would be for #2 to take some time to figure my sh!t out and work on myself, and for #3 talk to more women and spin more plates.
Of course this is easier said than done, but if I were in your shoes, I would go no contact and figure out what is causing me to obsess over a particular woman and go from there.