1. Amanda is wearing big earrings. She is wearing high heels, too.
2. Amanda is wearing not only big earrings but also high heels.
3. Amanda is wearing high heels as well as big earrings.
4. Amanda is wearing both big earrings and high heels.
(Are they all the same in meaning?)
Yes, they all mean the same thing.
Sentences 2 and 3 need commas, though, to be absolutely correct. In 2, put the comma after "earrings" and in 3, put the comma after "heels."