、。
She's busy at the moment, so she can't speak with you.
Literal
She [topic-は] now busy [because-ので], you [with-と] honorific-talk cannot.
~ので is one of the two main 'because' connectors, alongside ~から. The textbook distinction is that ~ので feels softer and more reasoning-as-circumstance ('given that...'), while ~から sounds more direct ('because...'). In refusals and apologies, ~ので is the safer pick because it backgrounds the reason rather than putting it in the listener's face. After a na-adjective or noun, ~ので requires な (静かなので, not 静かので) — but i-adjectives like 忙しい attach directly.