Yesterday the Simpson sisters–Ashlee and Jessica–threw a little soiree to celebrate their first-ever design collab: A line of clothes for tween girls. The line is for ages 7-16, and this demographic made up most of the crowd at the party at Dylan’s Candy Bar.

I was very jealous of these girls for two reasons: First, they got to decorate and bedazzle jeans and shoes. Second, they got to eat all the candy and mini grilled cheese sandwiches they wanted, while I just stared longingly–wrong week to start a juice cleanse.

Ashlee was there with her adorable son, the curly-haired towhead Bronx; Jessica worked the crowd signing autographs and taking pictures with mini-fans while attentive babydaddy Eric Johnson stayed close by. We waited very patiently to grab a few words with the mom-to-be, who was wearing towering heels and a short leopard print dress.( We overheard her telling several people that flats hurt her feet and she’ll wear her heels as long as possible.) When we finally got to her, she dished to us about working with Ashlee, her new design projects, and finding out the sex of her baby:

Fashionista: Is this the first time you’ve worked with your sister to design something?
Jessica Simpson: Ummm. I guess, yeah! But it feels like we always work together!

Whose idea was it?
This was my mother’s idea actually. My mother thought it would be great to combine both of our styles, both of our personalities.

How would you describe your separate styles?
Ashlee’s very rock’n'roll, very cool, very boho-chic. I’m more of like your all-American girl. I’m pretty classic, I’m pretty easy going. Combining the two is always fun. But I am the person that does like to wear something simple and throw a crazy accessory with it.

Did you have any fights or creative disagreements when you were designing the line?
No! We did not. We loved being in the approval meetings together, we loved inspiration shopping together. It’s been fun. I feel like all these little girls are wearing stuff that Ashlee and I would both wear. {Ed note: The girl models running around looked very cute in faux fur vests and 70s floppy hats.}

So Ashlee has a boy. Do you think you’ll ever do a line for boys?
We want to do baby, kids. I’m gonna do maternity.

When will that happen?
We’re looking into launching around February, but we’ll see.

There’s been a lot in the press lately about girls being made to look too “sexy.” Did you think about that?
We made sure that they can look adorable but stay their age. I think that keeping it age important is extremely important.

So do you know what you’re having? (at which point I rudely pointed at her belly)
I don’t. I find out on Monday. I can’t wait to go home to find out!