Complex sentence: She's superhumanly strong which allows her to swing her extremely heavy halberd with ease; she is also very fast and agile with centuries of combat experience, and her presence and status as an apostle is a great help to Itami's group in establishing social relations.
Split into simpler sentences: She's superhumanly strong, which allows her to swing her extremely heavy halberd with ease, and very fast and agile with centuries of combat experience. Her presence and status as an apostle is a great help to Itami's group in establishing social relations.