One common theme is redemption. The woman with the scar might be trying to overcome her past, and the ranch and the love she finds there could be her path to redemption. Another theme could be acceptance. The male lead accepting her despite her scar shows a powerful message of love being more than physical appearance.
Well, often there's the theme of transformation. The ranch environment is new to the woman with the scar on her face. Through her experiences there and her relationship, she transforms into a more confident person. Also, there's the theme of love conquering all. No matter what has caused the scar, the love she discovers on the ranch overcomes any insecurities or obstacles related to it. And sometimes, there's a theme of family. Maybe she finds a new family on the ranch, people who support her and her relationship.