The translation above, "She runs around the park.", is wrong. If you listen to the recording of the sentence in Hebrew the stress is at the beginning of the word. That would make it past tense in this case. "She ran around the park."
Well, both are used as prepositions. They are synonymous, מִסָּבִיב לְּ־ is a case of prepositional stacking (get UP ON OUT FROM UNDER that table), whose meaning later paled, so that from around to fossilized to simply mean the same as סְבִיב.