Totally normal part of development
They go through phases of identifying with and being close to a same sex parent, and phases of needing to be close to opposite sex parent - or parental figure.
It's how they learn to develop various aspects of their own personalities and understand them and how to socialise with others.
It's definitely not personal, but as you said yourself it's possible hormone fluctuations are affecting you
I well remember a friend of mine breaking her heart the first time her eldest said "I hate you" she totally took it to heart. Before being a mum she hadn't very much experience with kids at all, I reassured her that it's just the way toddlers are sometimes.
A few days later my own dd said it while we were with them and I'm far more used to the fickle and capricious nature of young children and I just went "yea well I don't like the way you're behaving right now either, time out dd! Over on that bench" (we were at a park), couple mins later after the time out big hug "sorry mummy" "thank you dd now off you go and play" all done and dusted.
Pay no heed to it
It's almost off topic, but not though.
Her dad needs to stop Disney dadding. It's not good for her long term and it's not fair on you to make you always play "bad cop" it can store up problems for the future. Have a chat with him about this.
Children need parents - not more friends, they'll have thousands of friends in their life they only get 2 parents.
Boundaries and discipline are necessary to not only raise well behaved children, but so that they feel safe, secure and loved.
Kids that are allowed to run rings around a parent don't feel secure or loved, I've seen the damage this can do up close.
Once a friend of dds from a "chaotic" home was at ours for dinner etc and I overheard dd moan (as teens will) about me being "strict" about curfew. Dds friend turned around and said "I wish my mum was strict like that! Half the time I think she couldn't care less if I came home at all!"