Of course they will read magazines and want to buy make up. Choose your times and chat with them about their day, their friends, listen to their feelings. Remember that none of us feel very secure when we don't quite know how to be. Advertising, social media, pressure at school - all these things impact self -esteem, body image and worries about being popular.
This is your perfect opportunity to have conversations about sexism, about alternative ways of viewing the world, about movies, blogs and books, which differ from the diet of glossies and celebrity gossip our teens are fed. This doesn't mean challenging all the time. But it does mean being conscious of the world your children live in. For example, of course your daughters will want to feel attractive - try making comments like "you look lovely, your eyes really sparkled whilst you were singing" or "You moved so gracefully at the gym competition". Making an effort to link their questions about appearance to an action is a subtle way to alter the endless diet of teen celebrities body image obsession.
Talk to them about what they secretly think about Kim Kardashian and Miley Cyrus. What do they think about Lorde and her lyrics?
Link conversations about study with their thoughts about their dream job. If they want to be a makeup artist, as teenage girls often do, then try stretching the conversation a bit wider into examples of creative women and how they got there.
Be very ready to do deals - some time at the mall in return for some study and chores. Negotiate on boundaries and curfews and your right for safety checks about where they are, who they are with, cell phones left on. Put the agreed contract on the fridge.
When they were toddlers you let them learn to walk. Remember how you had to let them move away from you with all their curiosity at this brave new world they were entering? But you kept an eye on the duck pond they were toddling towards. And they grew more confident because they knew that you were somewhere near them.
It doesn't really change.
Boys, parties, selfies with faces caked in makeup and how many "likes" they got on Facebook are variations on the standard themes. Don't worry too much about their current focus. But do use it for discussions linked to wider issues.
And remember, although they may not always demonstrate it, you are their most important role model and your ongoing love and guidance is what they really crave. So find the balance between unnecessary criticism and necessary guidance.
And be patient with yourself, having teenaged daughters is a first for you as well.