Parashas Acharei Mos · Passuk 18:13
Chabad.org — English translation + Rashi
Torah Temima treats the maternal aunt in parallel to the paternal aunt (Yevamos 54b pattern).
English: “Your mother’s sister” — whether maternal or paternal side of the mother.
Maternal aunt — both sides
The mother’s sister is forbidden regardless of whether she shares both parents with the mother.