The "Beginner Ballet Routine" is crucial to decrypting this letter.

Look at what's underlined in the "Beginner Ballet Routine".

This is a skip cipher. In a skip cipher, you only read certain words in an encrypted message. A skip cipher can have one key (e.g. if the key is 3, you would read every 3rd word), or multiple keys (if the keys are 3, 10, 12, you'd read the 3rd word, then the 10th, then the 12th, and repeat).

Each line in the "Beginner Ballet Routine" tells you which word to read. Start at "Hey" (that's word #1).

Notice that two numbers are underlined in each line. If one number was underlined, you'd just skip ahead to read that word (e.g. if "two" is underlined, read the 2nd word). Each line corresponds to one word. Do not add the two numbers in each line together — combine them in a different way.

Multiply the numbers in each line together, then read that word. For the first line, the numbers are 8 and 1 ("first"), so 8*1=8. Read the 8th word. For the second line, the numbers are 4 and 2 ("second), so 4*2=8, so read the 8th word again (after the word you just read. The first two words in the decrypted message are "how about".

Decrypted, the letter reads:

"How about valium instead of melatonin? That will do her in for sure."