If you think of it in this way, it makes more sense.
Are you doing her talents any justice by keeping her? If your interests arent the same, you are holding her back. She could be a great hacking horse or a good dressage horse with someone who has an interest in that sort of thing.
I have a QH that is fabulous. I love him to pieces. He is a trained barrel horse and is very fast. He loves his job. He has a huge amount of talent in any speed competition. I am a trail rider. I love to trail ride. Nico doesnt mind it, but he'd much rather be flying around turns and putting his head down into a run. While I love him, I am doing him no justice by making him do something that isnt really great for him.
Leasing or loaning can get difficult. People are unreliable and some will say they are taking care of her and paying her bills when they are not. While Im sure you do love her, I would sell her outright. Find a great buyer, be picky and make a good decision for her.