She doesn't say that at all. Someone actually has her quoted verbatim earlier in the thread (EDIT: That might actually be in the thread in the Xbox forum but whatevers ...). Basically she tells you to "put it to good use" and that's pretty much a direct quote.
She never ever says you won't get another one. Try again.
She never ever says you won't get another one. Try again.
Like I said, it's been awhile since I played the Thieves' Guild quests, so I may not be remembering correctly... Anyway who cares? Don't be in too much of a rush to complete everything... it spoils the game.