If she is a purebred or mostly all dairy, then treating her as a beef cow will not only ruin her udder but you will have problems with the calf getting too much milk and scouring will most likely be frequent. I bought a jersey heifer that had mastitis before she calved, and when she calved she had no milk in that quarter. She had her calf and I milked once a day and got over 2 gal a milking with the calf on her all the time. The calf scoured for about 2 weeks from the over abundance of milk and the richness of it. The thing to do is either find at least one more calf, preferably 2, to go on her and use her as a nurse cow, or at the least milk her once a day and don't feed her any grain so her production will be minimized. She is a dairy cow for a reason, she is supposed to be milked. Some produce better than others, but they are not designed to only raise a single calf. If she gets mastitis, then the calf sucks, it could get sick from that also. And if she gets mastitis and it doesn't get treated or she isn't kept milked out then it could go systemic and you could lose the cow. At best it will cause her to lose a quarter or two....
Also, it will be tough on her to keep her condition by treating her as a beef cow. They are designed to put alot into initial production and will drop weight for the first several months into production and even if she adjusts to only feeding her calf, will lose weight and probably not breed back as soon.
Watery scours could also indicate another bacterial problem/infection in the udder. Staph, strep, or e-coli will play havoc with the calf's system and can kill it. Did you get the jersey to be a milk cow then change your mind about milking? If you don't want to milk her and don't want to put calves on her then maybe you could trade her off to someone wanting a milk cow in exchange for a beef cow or sell her out right for a family cow, and buy another beef cow.
I have several jerseys and guernseys that I use as nurse cows, and even their half angus daughters often make more milk than one calf can use.