I agree with this.
Grass is always greener somewhere else, until it isn't. I bet even money she tries to come back. Some women just cannot pair bond. If things are going too well, they wreck the relationship on purpose. I think
@Medina is right too about you being too predictable and "safe." Women need stimulation. According to Tony Robbins, the first two core human needs are
Certainty and Uncertainty https://www.habitsforwellbeing.com/6-core-human-needs-by-anthony-robbins/. I think this is amplified in relationships and with women in their lives. Women are always craving "excitement."
I don't think she cheated either. And even if she did, most women won't leave a 10 month relationship over some ONS or fling. If she takes an ex back who saddled her with $40K in debt, she's the type that craves abuse and mistreatment. If this is the case, she did you a huge favor.
Let us know how it turns out.
Good luck.