Dear aspirant

This is an easy calculation

She had got total of 4 marks.

From which you told she done 3 correct answer means she got 3× 2= 6 means she scored total 6 marks for correct answer.

Now if we calculate wrong answer then she had scored 2 marks lesser than correct answer marks which means that is negative marking, Means -0.5 marks (for each wrong) × 4 (no of questions wrong) = -2 ( total negative marking) so she had answers four questions incorrect.

For scoring total 4 marks she had answer 3 correct answer and 4 incorrect answer.

Hope this was helpful for you

All the best