“This is she,” is correct. When using a linking verb like be (is), the pronoun becomes reflexive back upon the subject noun. In such a case, “she” is not the object, it is reflexive back upon “this.” This is what’s called a predicate nominative. Now… if you use a regular action verb (sees, greets, kills, comforts, etc), the pronoun becomes a direct object. In such a case, it would be “her.” Throw everything out the window of you subscribe to the modern “woke’ pronouns, which make a mockery of proper English. I digress…