Personally it looked to me that the question was asked and answered, unless I'm missing something the only question I saw in the original post was "am I to big to break this mini?" The answer "no". Instead of getting mad the follow up question should have been "how do I train this horse w/out riding?" My advice would be train it to ground drive, then train it to accept the saddle. The rest should come pretty naturally. You want to expose her to as many different things and situations you can. One of the biggest obsticals for a horse over come for riding is having someone above them, minis and small ponies are at an advantage because people are always above them!
What she is most likely objecting to w/ the saddle is the tightening around her girth, once she's good with that she will probably not mind a small child on her back. And training her to ground drive will prepare her for the point when the kid is ready to ride solo.
I also took some offence to the statement that all ponies are bitches (and found it alittle funny to find this is in fact a pony!!). I personally have owned 5 ponies and one half pony mule. One would take advantage if the rider was not in control, but was otherwise the perfect pony w/ someone that knew what they were doing. All (including her in my opinion) where excellent ponies! (and fyi all but the mule where mares, gelding vs. mare is just personal preference). My current pony is about as perfect as they come! (and I'm only selling her for $500).
I, personally, would never buy a mini for one of my kids, not because they aren't lovely animals and can't carry a small child, but mostly because I wouldn't want to have to upgrade in just a few years.
And lastly, since I'm not sure it's been said, she's a really cute pony! I'm glad you saved her and I think with some training she will be a good match for your cousin! Even if he only gets to enjoy riding her for a few years (I guess after that you could train her to drive).