。
She bought her son a camera.
Literal
She [topic-は] son [to-に] camera [object-を] bought-for-him.
~てあげる is the benefactive 'do for someone' auxiliary — here 買ってあげる ('buy for [him]') marks the purchase as a favor for the son. The recipient is the son (に-marked) and the speaker is empathizing with the giver (the mother), so あげる is correct rather than くれる. カメラ is a katakana loanword from English. Note that ~てあげる can occasionally feel patronizing or self-congratulatory if used about gifts to social superiors; here, parent-to-child is the natural register.