Might be overwatering. They usually don't yellow like most leaves do when the pot has too much water. Also, consider transplant shock, as that can also weaken a plant. Facing north is a bit low in sunlight, facing east, west, or the best south exposure is better. Rosemary is a sun lover. To check for moisture, you can usually tell if its too much if teh soil surface is still damp a day after its watered. Many people kill plants becase of over watering. Not sure what kind of soil was used in transplanting, but the soil should be sterile so no bugs or fungus is in it.

the repotting might not have helped - they're fine with cramped quarters for the most part, but they insist on good drainage - and if the larger pot allows for better water retention, chances are good her roots have started to rot.

the brown could also be frostbite (from being too close to a cold window pane) or heater burn (from being too close to the heat vent, radiator, or over the baseboard) - I'd let the soil dry out, make sure it has good drainage, and give it more sun a little at a time.

If the soil mix is soaked, slip the plant out and into a dry mix. Keep the soil just moist--no sitting water. Brush away the dry needels to open the plant up to air circulation. Take a small scissors and trim back the brown branches a half inch at a time--until you see green tissue. Get the plant into bright light or under a grow light until you can set it outside in full sun. If it's for indoor growing--get it into the brightest window you have.

Here is a link that might be useful: http://HarvestToTable.com

I was given a rosemary tree a few years back and did great unitl spring and it just up and croaked without any change in the way I cared for it nor did it get repotted. Was dead within a week. No signs of problems anywhere.

Some rosemary types do not last long. Here in Z6 my rosemary outdoors will not survive winters, yet some types do. I start it from seeds.