What is the semicolon doing in this sentence?

Emily loves milk, but she can’t drink it; she’s lactose-intolerant.

(1 point)
Responses

It’s separating items in a complex list.

It’s uniting two closely connected clauses.

The semicolon in the sentence "Emily loves milk, but she can’t drink it; she’s lactose-intolerant" is uniting two closely connected clauses.