You will clean her graffiti from the 3 famous paintings, then destroy her own.
Before you can go to the Widow's dream, get the Stopwatch and the Turpentine from the chests in Captain Crawfish's dream, and the Paint Sprayer from Dr. Hare's dream. Use the turpentine in the sprayer and equip it to clean the paintings in Black Widow's dream. After you talk to the Black Widow, you will shrink onto the surface of each painting, Dodge the Spiders, and spray the red letters to erase them. You will also find some Shrinking Potion on the first painting (upper left) and the Crystal Key on the second one (upper right).
When all of the paintings are completely cleaned, the Black Widow will attack you. Avoid her long enough to spray her own self-portrait until it dissolves, leaving the Paint Brush Totem.
Black Widow's totem is in her dream after you clean the paintings and destroy her painting.
The Crystal Key is in Black widow's dream. It is on the first painting that you clean.
There are 4, one from each super villain's dream. (see related question)
You get the shrink potion from the black widows dream.
There is no actual gold on Super Villain Island. The Golden Carrot totem is at the bottom level of the anthill in Dr. Hare's dream. You need the Diamond Drill from the Binary Bard's dream.
The sprayer is at the bottom of the second level of the anthill in Dr. Hare's dream. You need the turpentine from the upper chest in Captain Crawfish's dream.
You need the Crystal Key from Black Widow's dream. It is at the upper right of the second painting you clean.
It is on one of the paintings in the Black Widow's dream. Specifically on the second painting (Starry Night) near the upper right.
Use the Stopwatch from Captain Crawfish's dream.
you dont. you can get a spray bottle from Dr. Hare's dream, turpentine and a stopwatch from Captain Crawfish's dream, a diamond drill from Binary Bard's dream, and a crystal key and shrinking potion from the Black Widow's dream.
The key is on one of the paintings in Black Widow's dream, and you can get it while you are cleaning them. It is in the upper right corner of the middle painting (Starry Night).
You use it to get into the "ship in a bottle" in Captain Crawfish's dream.