More problems getting on the horse

Question

Did a quiz, apparently answered wrong, and am now very confused.

The question: Elle ________ monté le poney de Jérémie et il a été très docile.

I went with "a monté". The quiz says the correct is "est monté".

Going by the Q&A, it seems like my answer was correct. I am stumped in two ways.

First, the Q&A says that avoir followed by the past participle is used for getting on a horse. This is a (pro)noun followed by a direct object. The lesson uses the example a "a monté mon cheval". I'm struggling to see why the verb auxiliary would switch based on who owns the horse.
Second, assuming I have the first part wrong someone how and être is the correct auxiliary, should the correct answer not be "est montée"? The subject is feminine.

Accepted Answer

Hi Cameron, 
I have checked the Kwiz and the correct answer given is
'a monté'
which is right so if the problem persists please use the Report It button on your correction board which will link directly to the kwiz in question.
Bonne Continuation!

Answer

Hi Cameron,It looks like there is a fault   --  I believe that you are correct."Elle a monté le poney ....." means that she got on / mounted the poney.If the text had been written, "Elle est montée sur the poney" that should also be correct but in the situation that you are querying there is no preposition, so you are dealing with a direct object therefore avoir is appropriate.The only slight concern that occurs to me is:  It is possible that to write "Elle a monté le poney" could mean that she lifted the animal up? I'm intrigued to see what the other commentators may think.Hope this helps.Jim