。
Yoshiko is studying like crazy.
Literal
Yoshiko [subject-が] scratchingly studying.
がりがり is a mimetic that describes intense, almost obsessive effort — the same がり that gives us がり勉 ('grind, study nerd'). Here it modifies 勉強する to convey furious, head-down studying. The sentence is beginner-level structurally but the mimetic adds color.