When you use って, how do you differentiate who is part of the quote from who made the quote? For example: 彼女はかわいいって/She said かわいい or 彼女はかわいいって/someone said she's cute
As mentioned in the comments, if you are speaking and really want to disambiguate you have a couple options, like moving the sentence constituents around or using explicit quotes (although the latter only works in writing and the former can sound awkward).
However, I think the real answer here - as sundowner mentioned - is context. Assuming your native language is English, it's worth mentioning that you do the same work all the time in English. If I say
I told him that he couldn't drive home because I knew he was drunk
This sentence is ambiguous as whether I actually told the other person I knew they were drunk. (I.E. did I say "you can't go home" because I knew they were drunk, or "you can't go home because I know you're drunk"?)
This ambiguity can be resolved by adding context like
but didn't want to call him drunk or conversely
but he denied being drunk; generally the idea is that if the distinction is important it will be obvious from context, and if it's not obvious it's either not important or you just have to ask.