I few days ago I published an article about my confusion about how to deal with people gifting adult clothing to my 6yo daughter. I had asked for help with that, and the HIVE system responded differently than I had expected. I didn't get many direct replies, but luckily 
Long story short - The Hive delivered. In an unexpected way, but I see a lot of things a lot clearer now, and I'm very thankful for that. So, here comes the conclusion:
Taraz wrote in his comment:
We keep it practical for our daughter, and she generally makes practical decisions about what she wears, depending on what she is doing.
Children make decisions based on what they see and are taught. They're not free in any way, they're bound to their upbringing. As a father, I have the responsibility to teach her what to wear, what is adequate in what situation. Be pretty on weddings - but have a change of clothes that you can absolutely destroy while playing after the ceremony.
The dress we wear gives the very first impression of our personality or who we are, and decent clothing is very much necessary for adolescents earning them self respect. Otherwise the society is always full of evil - its easy to earn their attention, by dressing wicked.
Having done my studies in a very left-leaning environment, I saw wearing whatever as a statement - against patriachism, against objectifying women, and so on. But it's not that easy, there's a lot of grey area, and many different angles to look at it. What I derived from the last days of thinking and reading is: As a parent, my responsibility is to teach her that her personality is not tied to what she wears. It's a tool that she can use in many ways, and each way she dresses has different consequences. She has to be aware of what might happen, how people will see her.
The real empowerment in clothing is not proving power over e.g. men's sexual desires, but know what to wear in what occasion to achieve the desired outcome. But that as well has to me guided and managed in order not not create a manipulator, because:
What you will not see in those words is "freedom from consequence", meaning that while people can act however they want, there is still a cost to their behavior.
This phrase is almost a summary of Taraz' post. I had posted my own argument regarding responsibility a while ago, in this post, arguing that real freedom lies in taking responsibility for one's own acts and the consequences, as we do not rely on others anymore to take the blame. Being aware of one's state as an individual is important, but so is being aware of one's state of being an individual within a society.
I will not be able to teach her about every consequence. Especially right now, most consequences are out of her ability to comprehend, so I have to work with simplification and/or the "that's adult clothes". And if she's too young to comprehend, she's too young to decide, and too young to take responsibility - so it's my responsibility, and I have to defend my choices. I have to be coherent between my choices for her and my values.
Unschool answered to my post:
During adolescence, everything you wear is associated to personality. I really think before and after that period, it doesn't really matter what you wear.
It's more about what you do.
Both Unschool and sanjeevm write about something important: self-respect in puberty. The more I can teach Lily to not see superficial things like clothing and looks as important to her personality, the easier she will have it in puberty - it's still going to be a legit nightmare, but the more I can prevent, the better.
There are many ways to express oneself, and yes, clothing is one part, but there are way more effective ones. For me, it was writing, music and reading during puberty. I have to help her find her own forms of expressions.
Thanks to everyone who answered. I was able to get my head straight on how to deal with it, more or less. Next step would be how to make her mom understand that, but that's a different topic and a lot more complicated...
