That looks quite high, but unfortunately is not uncommon in a new tank which is beginning a cycle. You said your gf kept a 5g? Running a new filter for a few days sometimes produces some cloudy water as beneficial bacteria establish a colony. I am not sure on the specifics but as a tank begins a cycle, usually the ammonia and nitrite spike to lethal levels. Then, some tanks don't at all.
I would say this is your problem. A new tank trying to cycle, using Squishy's poop as an ammonia source and then spiking and killing him. This is a hard way to see them go, it happened to me with my first betta Lakitu. He is buried now and currently thawing in the spring ground and leeching into the tree in the backyard.
It's easy for me to say not to give up. I know losing one fish is hard but I suggest running the tank still so it can balance its levels in time if you change your mind.