。
She felt her body being lifted up.
Literal
She [topic-は] body [subject-が] is-being-lifted-up [nominalizer-の][object-を] felt.
Layered structure. The inner clause 体がもちあげられる ('the body is lifted') is in passive form — もちあげる ('lift up') → もちあげられる. That whole passive clause is nominalized with の and made the object of 感じる ('to feel, perceive'). The pattern [clause]+のを感じる ('feel that X' / 'feel X happening') is parallel to [clause]+のを見る ('see X happening'), ~のを聞く ('hear X happening'). The が inside the relative-like clause marks 体 as the subject of the passive event.