I would be getting her vetted before even contemplating jumping or dressage. My boy has got a bone spur and arthritis in his hock, I started noticing that he 'wasn't right' because he was unwilling to go forward, was grumpy and not willing to travel to the left. No one could pick up any lameness in his movement and said he was just 'testing me out'. I went to get him xrayed and sure enough, his hock is a goner.
He is now mostly paddock sound, after months of VERY expensive ongoing treatments, and I can pleasure ride him but that's about it. He will never be able to cope with the stress of jumping or the degree of collection required beyond preliminary level dressage.
Please make sure your mare is sound enough to do these things, as you may be putting her through unnecessary pain.