。
She's becoming cuter and cuter.
Literal
She [topic-は] increasingly cute-seeming becoming-goes.
かわいらしい is かわいい with the suffix ~らしい ('having the qualities of, -seeming'), which softens it to something like 'sweet, charming, lovably cute' — slightly less brash than plain かわいい. ~くなっていく chains the change-of-state ~くなる with the future-progression auxiliary ~ていく, giving an unfolding 'getting cuter as time goes on' feel.