As 'pretty' is an adjective, we can only make it stronger with 'very' or an adverb such as 'extremely', 'absolutely'.
We use 'much' with an uncountable noun, and usually in the negative. "She doesn't have much education."
However, we can use 'very much' to show that we agree with a comment featuring an adjective. Example "She's pretty!" - "Oh, yes! Very much!" or "That exam was so difficult!" - "Very much, yes."