。
She is wearing long boots.
Literal
[topic-は] long-boots [object-を] is-wearing.
Japanese has a small family of 'wearing' verbs that pick out the body part: 着る (torso/dress), 履く (lower body and footwear — pants, skirts, shoes, boots), かぶる (head — hats, helmets), はめる (small tight items — rings, gloves), する (accessories — ties, scarves). Here 履く is the right verb for boots. The ~ている form ambiguously denotes either 'is putting on (right now)' or 'has put on (and currently is wearing)' — context decides, and for clothing it's almost always the latter.