"Was that (she, her) on the patio?"

I think her?

"She" is correct. "Was" is an infinitive verb with no direct object. "Her" is the objective form, "she" the nominative form.

I think Reed means that "was" is a linking verb, but the result is the same: Linking verbs are not followed by direct objects (objective form), but by predicate nouns or adjectives (thus the nominative "she").

http://www.chompchomp.com/terms/linkingverb.htm

http://grammar.ccc.commnet.edu/grammar/objects.htm#predicate

To determine whether to use "she" or "her" in the sentence, you need to identify the correct pronoun to refer to the person on the patio. Here's how you can figure it out:

1. Identify the subject: Look for the person or thing that is performing the action in the sentence. In this case, the subject is "that," which refers to the person on the patio.

2. Determine whether the person on the patio is the subject or the object of the sentence: If the person on the patio is performing the action, then she is the subject. If the action is being done to the person on the patio, then her is the object.

In this sentence, the person on the patio is not performing the action, but rather being referred to. Therefore, the correct pronoun to use is "her." The correct sentence would be: "Was that her on the patio?"