Do Donkey's make good pets?

My 6 year old daughter has her heart set on getting a Donkey as a pet. I try to get her whatever she wants, when she wants as the consequences of not doing so are not worth the hle. I do have a couple of reservations though, our garden where the mule would be kept is only 5 metres by 10 metres. In addition she wanted a dog a year ago, but we had to have it put to sleep after she lost interest in it after 3 weeks. I fear the Donkey would suffer the same fate.