After the events of the game you are probably just with Monika for several days but she realizes that you are definitely not happy so she changes the game codes again and now gives you the option to talk to her

After she explains it to you, she looks at you with an insecure look while some tears roll down her cheeks and speaks desperately

"Y-You love me right? You wouldn't leave me alone, right? RIGHT?"

Based on Monika's appearance, what she's most afraid of is that she'll make everything go back to normal, the girls will all come back and you'll leave her alone and choose another girl.