。
She's thinking about going to Europe this summer.
Literal
She [topic-は] this summer [in-に] Europe [to-へ] go [thing-of-こと] [object-を] is-thinking.
~ことを考える ('thinking about doing X') is one of the standard frames for 'considering doing.' The verb is nominalized with こと and made the object of 考える ('think about'). The polite form 考えています here is the resultant-state continuous, marking the deliberation as ongoing rather than a single moment of thought. Note the layered particles: この夏に (time-when), ヨーロッパへ (direction), 行くこと (nominalized action) — each piece pinned with its own grammatical role. ヨーロッパ ('Europe') is a Portuguese-origin loanword that's been in Japanese since at least the 16th century.