Obviously Empress Frederick, who was an implacable enemy of the 'fringe', wasn't able to exert enough influence to talk her out of that on her wedding day. 
I think it really made poor Margaret look rather frumpy on her wedding day. The dress was a beautiful, if overdone by today's standards, Victorian concoction but her hair looks rather blowsy.
Yes, mothers traditionally helped with the dress (they probably had more influence then than today) and definitely with the trousseau since it would contain 'grownup' outfits and unmentionables. In the case of Princess Alexandra, her mother would've had sway if not for the fact that she was marrying the heir to the British throne and Queen Victoria's wishes (as per usual!) took precedence over a mere 'Princess mother'.
The Empress Frederick had a down on fashionable fringes, but there seems little else which was worn at that period and Mossy would have felt horribly underdressed if her hair had not met the basic fashionable standards of the time. But I would agree the whole effect, hair and dress, is heavy and far too elaborate. I've never been certain of the Empress Frederick's taste - she never looked terribly well turned out in my view, all her clothes looked rather too heavy and elaborate as well, and I wonder if she held sway over the dress design.
With regard to Alexandra's trousseau, I think the charge of interference is a little unfair to Queen Victoria. The lace dress King Leopold gave was a wedding present, and although
he intended it to be worn by the bride, there is no indication that it had been specially requested by the Danish royal family nor that it was actually rejected - presumably it was available for other uses than bridal. The majority of Princess Alexandra's trousseau was made in Denmark and there is no evidence that Queen Victoria had a say in it of any kind (or showed any inclination to do so). The replacement of a Brussels by Honiton lace dress was essentially political - a bride this important to Britain should be wearing completely British manufacture. Princess Alexandra and her mother understood their duty in relation to her future position as the Princess of Wales and basically accepted a substitution, they weren't ridden roughshod over an entire trousseau.
