Where did Jill end up?
Jelly, 3 bytes

SĊṆ


Input is in form of complex numbers, which will be real or purely imaginary.

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How it works

SĊṆ  Main link. Argument: A (array of directions)

S    Take the sum of A.
 Ċ   Get the imaginary part of the sum.
  Ṇ  Take the logical NOT of the imaginary part.