My mum thinks this dress isn’t right for wedding- is she right?

Is this a little too informal?

Trying to find something half decent to wear to a wedding is not easy. White is obviously ruled out. You don't want to wear something too flashy and risk upstaging the bride, but you don't want to look underdressed either. One woman faced quite the dilemma when her mother told her the dress she picked wasn't appropriate. She explained to Mumsnet that she was attending a wedding in a couple of weeks. She wasn't sure what to wear because she has usually been a bridesmaid. She found a short, pink dress that she loved but her mother said it wasn't good enough. "Going to a wedding in a couple of weeks. Saw a gorgeous bardot dress, loved it. "My fiancé loved it so ordered it and I love it in real life too." "However, I sent a pic to my mum who just texted back "I don't like it for a wedding" then didn't say why or anymore? "Am I breaking some kind of etiquette? Clueless about these things. "For most weddings, I've been to I've been the bridesmaid or the bride and don't have a clue how guests dressed. Many people agreed that the dress was too casual. One said, "I'm a great believer in women dressing however they like, but this isn't really wedding attire. It's a nice dress but more suited to a beach holiday than a formal occasion." Another said, "It looks like a beach coverup." "I wouldn't care if you wore it to mine. It's not my personal taste and is perhaps a little bit beach cover up/casual for a wedding -but it's fine." What do you think?