"That is hers."
Quick question: Does もの basically mean "thing"? I've noticed it in a few other words like 食べもの and のみもの which mean "food" and "drink" respectively, right? This leads me to think もの pretty much means "thing" like "thing to eat" or "thing to drink." Or am I completely up the wrong tree?
Yes, and you often see it written in kanji as 物. Don't know why it's kana in this sentence actually... There are many verbs that can be turned into nouns by adding 物 after the い-stem of the verb.
Some Examples 食べる 【たべる】to eat (verb) 食べ物【たべもの】food (noun) 飲む 【のむ】to drink (verb) 飲み物【のみもの】drink (noun) 建てる【たてる】to build (verb) 建物【たてもの】building (noun) 買う【かう】to buy (verb) 買い物【かいもの】shopping (noun)