In my opinion, if you are honestly trying to help, you need to know that what you are saying does
sound judgemental (even if you don't mean it to). I can understand that if a person is abusing, neglecting or causing suffering to a horse it is our responsibility to speak up, but you don't have a right to say that because they are a beginner they shouldn't get one. Everyone has a first horse. If your horse has had previous aggressive behavior, she may be affraid of him/her.
As far as age goes, we all know that green + green = black and blue. I can personally vouch for that statement!!
But age is just a number you can get a 20 year old that is hotter than hades and a 4 year old that is dead broke. They may buy her a well trained horse that is steady as a rock, and not experience the problems that you came across. And as someone else said, her parents will be responsible for the care and maintenance as well as her. Never know what their experience with horses are. They may have grown up on a horse farm or something.
Someone else said that affording a horse is not the same as affording lessons, I agree. And it is not your place, no matter what your intentions are, to say what someone can or cannot afford not to mention you have know idea what their financial situation is. It is very rude and you sound very catty. And as someone else also said, if your friend knew you were saying that she would be VERY mad and probably embarrassed.