Hmm, I'm not sure that's true, for a few reasons.
Prior to the tailoring revolution, clothes would take less time to make. A tunic is quicker than a doublet; you spend more time sewing on doing fiddly weird things than just running a seam, even by hand, and the fewer fiddly weird things in a garment the faster it is. So even assuming that all clothes production is on the farmer's wife's hands, before about 1500 she wouldn't necessarily have to spend the majority of her time on that.
But for most of human history, tbh, clothes were more frequently based on cloths woven to specific sizes and shapes than on pieces that were cut and sewn. Weaving would be a more likely profession than "tailor", although I don't think we can know how much weaving in antiquity was done by the woman of the house rather than younger women in the household.
There's also a host of activities associated with farming, like administration, preserving meat/other food, making wine/beer/olive oil/dairy products ... and there's no reason to think that men did most of that while women largely produced clothing. The Oxford Handbook of Women and Gender in Medieval Europe says:
This type of argument is undermined by the clear evidence that women did agricultural work in the fields. Late medieval sources such as Fitzherbert’s Book of Husbandry (1523) describe women’s responsibility for marketing butter, cheese, poultry, ale, and other items they produced, as well as taking grain to the mill, activities that also took them well away from the house. [...] Where evidence exists, women do seem to have been responsible for “housework,” but this routine work consisted of sweeping the floor, cleaning the few cooking and eating utensils, and preparing meals, often cooked in a single pot over the fire. The really laborious work done by women around the home involved processing raw materials into useful products: grain into flour, flour into bread, barley into malt, malt into ale, milk into butter and cheese, pigs into salted meat, wool and flax into yarn and cloth. In the late medieval period, many of these products, particularly yarn, ale, and cheese, were sold for cash. Both men and women worked to provide the family’s direct subsistence, and both produced goods for sale.
I definitely get the point of saying she'd be a tailor, but this goes right back to the original one, which is that a man who focused on these things gets called a farmer and the woman married to him who does the same things gets called a farmer's wife and/or is seen as doing "women's work".