Ashlee Simpson is ''really excited'' about her sister's wedding.

The 29-year-old singer will be bridesmaid when Jessica Simpson ties the knot with Eric Johnson next month and can't wait to be by the 'Dukes of Hazzard' star's side when she walks down the aisle.

She said: ''I don't know when it is. I'm really excited about it,''

Ashlee - who is engaged to Evan Ross and has five-year-old son Bronx with ex-husband Pete Wentz - thinks her sister has ''amazing taste'' and is overjoyed by the dress she will wear on the big day.

She added: ''My dress is really beautiful! It's really, really stunning.''

The blonde beauty has always allowed her sister to ''dress her up'' and loves borrowing her clothes when she wants to change her signature style.

She admitted: ''I've always borrowed her clothes. It's fun to go into her wardrobe and do something different because I'm half-tomboy, half-bohemian. It's fun to have her dress me up... I was either a doll for her growing up, or the one who messed her shoes up.''

When she isn't working, Ashlee loves spending time playing games with her son.

She told Us Weekly magazine: ''Bronx loves to boss everyone around on video games. He's just amazing at it. He's really smart and loves it, so of course Evan and I love to play with him.''