In my head cannon sweetie bot was a creation of the Autobots as a prototype minicon pretender and was sent to equestria but after a accident bumblebee movie style she lost her memories and always believe she was a pony until after a accident as all of his memories came back to her however during this time the Autobots and decepticons show up as well as a scared sweetie bot running in the forest and off a cliff by accident and woke up to find trailbreaker looking down at her and took her to their ship, some mouths later after the Autobots made themselves known to the ponies sweetie bot was more OK with being around the other ponies in this form however after a accident with water sweetie bot went in for a maintenance check but ratchet wasn't home but wheeljack was, sweetie bot around this time has been thinking of a possible upgrade, wheeljack wanted to start a conversation but sweetie bot is in a bit of a grumpy mood