Lady Stark tried her best to persuade Robb to pick a Northern bride. A northern girl was a flower of ice and cold, she could stand the dreariness and freeze of the North without wilting away. She begged and she pleaded, hoping to protect the summer warm Tyrell girl from the perils of the winter, but each time Robb reminded her that an alliance with the Tyrells was crucial in their survival of the upcoming winter. The crops of the summer hadn't been nearly as plentiful as past years and food would be scarce without the alliance of a southern bride. Mistakenly believing her pleas were to protect him from a loveless marriage, he made sure to assure her each time he and his wife would learn to love one another as she and Ned had.
It frustrated Catelyn, as she knew she could never tell him the truth, of what the North did to southern women. A southern woman needed warmth and sunshine and color and rain. They needed to be able to run after their children on soft green grass as they giggled and played. A southern woman's skin was not made for cold and therefore more often then not, trapped them behind the walls of Winterfell where the cold was less biting. It forced them to have to watch their winter children play in the snow without them. It was a cruel fate for a mother.
When Margaery Tyrell arrived in Winterfell, Lady Stark immediately saw the difference between herself and the youngest rose. The girl was manipulative, strong, cunning, with a mind for politics that rivaled many, but she was still a southern girl. She still hated the snow and cold and lack of color. The winter flowers were lost on her and the snow was wet and dirty and ruined the gowns she wore, to thin for the North.
In a way it appeared that Margaery was even more unhappy then Catelyn had been when she first arrived. Catelyn wanted desperately for Margery to be happy, to smile and laugh again as she knew from Sansa she once did. Gods know Robb tried his best to make her feel welcomed, but his efforts were hindered by his closer bond with his sister.
Sansa loved the North now more then she had in her youth. With the memories of King's Landing still fresh in Sansa's mind, the North was a welcome change and comfort. She had Robb wrapped around her finger. He spent his days with his people, writing laws and solving his realm's problems. He spent his nights in his sister's bed with his arms wrapped tightly around her in hopes of keeping her nightmares of Joffrey at bay.
It shamed Catelyn to know that she pitied the summer rose more then her own daughter. She thought that at least in King's Landing engaged to the mad boy king, Margery had been surrounded by a plethora of her father's men and her brother and grandmother. In the North she had nothing.
Catelyn was given some hope that the girl would make a home when Sansa's nightmares became more scarce (years after the marriage between Robb and Margaery) and Robb returned to his wife's bed. Sansa was merry and sweet once again and was quick to rekindle her friendship with the summer rose, unknowingly prompting other northern women to do the same. But still Lady Stark heard the whispers, angrily accusing Margaery of being more rose then wolf.
The castle staff knew better but the peasants still looked past her when they spoke, directing all queenly questions to beautiful Sansa, standing behind Robb with a circlet in her hair.
They didn't want a southern queen, they needed a northern queen.