。
She rarely goes out.
Literal
[topic-は] rarely goes-out-not.
外出する ('go out, leave the house') is a Sino-Japanese verb covering errands, trips, and any departure from home — broader than 出かける. Combined with めったに~ない, the sentence describes a homebody. In modern Japan, this profile (the 'indoor person' / インドア派) has gained cultural visibility alongside the 引きこもり (hikikomori) social withdrawal phenomenon, although they are distinct: インドア派 is a hobbyist preference for indoor activities, while 引きこもり describes long-term social isolation. Without more context, this sentence describes the more benign first situation.