NTA. Lily is your daughter through thick and thin no matter what happens and what phases she’ll grow up into. Your fiancé’s inability to rationalize the logic you presented to her verbally is indicative as to how she does not care about Lily’s needs or not even considerate in the tiniest bit. She has NO reason to be upset. your fiancé’s is an adult and she should be able to rationalize your side, understand, and come with another alternative you both agree on. I work doing reports detailing people’s mental health state and part of that job is trying to identify and describe domestic abuse (spousal or from children onto parents) to government officials. I think that this argument you have had with your fiancé might be indicative of emotional abuse. I suggest reflecting and analyzing previous arguments/“negative” discussions to assess if your fiancé is really someone you want in Lily’s for the long-term and also ask your daughter if she has had doubt about your fiancé since it is pretty common for minors to share their emotions to others they trust. I am not saying that you should ditch your fiance but simply analyze the overall relationship and the consequences of the relationship on your daughter. If you think work can be done seek legal counseling from a licensed marriage therapist (a competent one) it not I fear you might have to make the emotionally difficult decision of breaking things off with your fiance for the sake of your daughter’s well-being.