This sounds like maybe a touch of foot rot which you'll see in wet spring time conditions, especially if cattle tend to loaf in wet or low areas as daytime temperatures start to warm up. LA-300 at 3 mL/cwt plus some type of fungicide (like Koppertox) applied directly onto the foot and between the toes would be my recommendation. Foot rot might cause a distinguishable bad odor, but not necessarily so if it isn't an advanced case. If you can get your hands on that foot and get it up and look at it--clean it up enough to really see her foot--you'll wanna look for either signs of foot rot, an abscess, or a hairy wart. Any of those will cause lameness and could be the cause, but I don't think those conditions are as common. As somebody mentioned, it could also be a matter of her being stepped on by another animal which will probably just need some time. Good luck!