There are a number of famous TBs in the past that had linebreeding to very popular or famous sires, for sure.
Not every sire is great for line breeding tho, some had great decedents using that method, others had those descendants end up less quality than expected. The trouble is it takes time to figure that out
Destiny, Well I am not sure about the racehorse analogy you give. But yes, if you see the same sire 2 or more times in generations beyond the first 1 or 2, it is line breeding
Her mom is. Also weakest in movement, and a little down in scope and strength, so you may have issues with movement affecting her entire Dressage rating, and maybe have some trouble with the jumping end too