It’s not a double negative. Both negative words are active.

“She can’t not touch” means she is unable not to touch it, but is compelled to touch.

“She cannot refrain from touching it” perhaps seems more comfortable, but “refrain” also has negative force.

See John Lawler’s answer to Origin and correctness of “ain’t no”? for more on negatives and negative polarity.

It’s not a double negative. Both negative words are active.

Merriam Webster https://www.merriam-webster.com/dictionary/double%20negative defines double negative as

: a now nonstandard syntactic construction containing two negatives and having a negative meaning

"I didn't hear nothing" is a double negative

“She can’t not touch” means she is unable not to touch it, but is compelled to touch.

“She cannot refrain from touching it” perhaps seems more comfortable, but “refrain” also has negative force.

See John Lawler’s answer to Origin and correctness of “ain’t no”? for more on negatives and negative polarity.

It’s not a double negative. Both negative words are active.

“She can’t not touch” means she is unable not to touch it, but is compelled to touch.

“She cannot refrain from touching it” perhaps seems more comfortable, but “refrain” also has negative force.

It’s not a double negative. Both negative words are active.

“She can’t not touch” means she is unable not to touch it, but is compelled to touch.

“She cannot refrain from touching it” perhaps seems more comfortable, but “refrain” also has negative force.

See John Lawler’s answer to Origin and correctness of “ain’t no”? for more on negatives and negative polarity.