E.R.
My ex got remarried when my son was about 6. As a divorced mom about to get remarried in May to a great guy and stepdad, I agree with Deanna- you don't have to LIKE her- you just have to be polite to her in front of your daughter. I can see where the age difference would be a particular annoyance, lol. I am also sure that the Victoria's Secret and makeup, etc. are her attempts to be the 'fun' stepmom.
When my ex first got married to his current wife, every time she saw our son she would hug him and swing him around in the air and just generally 'overdo' it to such an extent that my then-boyfriend-now-finace and I would get back to our car and then burst out laughing because it was so ridiculous!
But I did realize that she was anxious for my son to like her and be comfortable with her and to 'establish' herself in front of other people as having a legitimate place in his life. She does- stepmom- but I am absolutely the final authority and have primary physical custody. So she sees him about 2 weekends out of the month. We do not always agree by any means ( mostly, I suspect because my ex pulls the wool over her eyes about things like he used to do to me, but cest la vie) but here is how I handle things:
1) Call her up and ask to meet her for coffee. A Starbucks or neutral territory, but someplace you can sit and talk uninterrupted. Meet with her on her own- no ex husband there. This is something honestly that you and she have to work out and he will only muddy the waters.
2)You don't have to like her, but try to see from her perspective to help you. She is younger, new baby, probably a little more insecure than you are. However, she also married a man who already had a child and committed to being a stepmom, so that says something good about her, even if she didn't really know at the time what that would entail.
Try to find things that you can agree on or feel good about talking to her about. For example, your daughter's school, or any other 'common ground' with your daughter, ballet lessons, soccer, etc. Chat about these things a little before you get into the big stuff.
2)Remember that she probably also has your daughter's best interests at heart. That said, I would just be honest and say " I wanted to talk to you because you are an important part of Susie's life, but I feel like we don't really get to communicate very often. I'd really like to feel like we are both on the same page about some things because the most important thing for both of us is that Susie is happy and safe and comfortable." She can't really disagree to that, right?
Start with things you know you both 'agree' about - like your daughter's bedtime, activities, etc. Then work up to things you don't agree with, but be careful how you bring them up- polite is the key thing here.
I would say something like " I know you meant for those Victoria's Secret underwear to be a fun gift, but I just don't really feel comfortable with her wearing them at her age. I wanted to talk to you about it because I didn't want you to feel like I was ignoring the situation, but I'm just not ready for her to be wearing things like that or playing with makeup for a few more years. I hope you can understand that."
Now- this is where a lot depends on her meeting you halfway. If she is reasonable, even if she disagrees with you, she will back down and agree with you and say that they were just playing, but she sees where you are coming from. If she goes on the warpath and gets defensive, all you can do is say " I am not trying to be critical of you at all. Parenting is really hard and sometimes we all make different choices, but this is really how I feel about my daughter and I'm just asking you to respect and understand that."
If she continues to be belligerent, well at least you tried. But remember- start with common ground, try to find things you can agree on, things that you both love about your little girl and go from there. When my ex moved in with his now-wife into her condo, I asked her to meet me for coffee. I was slightly acquainted with her, but didn't really know her. I told her I just wanted to know what my son should expect at her house- what rules she had, would he have his own room, things like that, so that the transition would go as smoothly as possible for HIM, when he was staying there.
Turned out she was the child of a very bad divorce,. she said that she thought my son was a really happy, well-adjusted kid and just wanted to help make sure things stayed that way. We are not friends- but even when we disagree, we have never yelled or fought in front of my son- not my ex, her, me or my fiance. We are all at least polite and can do school events, soccer matches, etc. together and present a united front of support for our son. Keep stressing to yourself - and to your ex and his wife- that THAT is your main motivation- your daughter's happiness and emotional security.
When we separated our mediator told me something that has ALWAYS stayed with me. She said:
"Your marriage has failed. There is no way around that. But- that does NOT mean that you have to fail as PARENTS. It is a totally separate issue and you need to look at it as such."
That advice has been so helpful over the years when my ex has been a jerk, lol. I still know he is my son's dad- and even though he isn't always the best or perfect dad, I try to remember that our son loves him. Same with his wife- it is sort of like she is an aunt that my son really likes and hangs out with. But I am always 'mom'.
Best of luck to you- please feel free to message me if I can help you out at all!!