I love you, I guess

She is just agreeing with you and doesn't really like you. You need to give her some space and be more there for her than usual. She might be angry and just might wanna be alone. Leave her alone and come back when it is time and feels right. You'll know it when you see it.

Him, "Love you babe ♥♥"
Her, "I love you, I guess"
Him, "What's wrong?"
Her, "It's uh nothing well I have feelings for someone else. I don't want you no more."