Hi Jaime,

There's not necessarily a ratio of hay to beet pulp unless you're not able to soak hay.  If you can soak hay - you want to figure out how much she should be eating per day and then use a minimal amount of beet pulp to get supplements in and the balance should be hay.  

You want to feed 1.5% of current weight or 2% of ideal weight - whichever is greater.  As an example - if she's currently 600lbs and her ideal weight is 500lbs you would do some calculating and see 1.5% of 600lbs is 9lbs and 2% of 500lbs is 10lbs so she should eat 10lbs per day TOTAL.  So if you feed 1lb of beet pulp the other 9lbs would be hay.