Would it be "tu misma" or "ti misma"?

Question

The sentence:

Nora, prueba este plato _______ [yourself].

The answer says "ella misma", but I definitely know that's wrong. However, I don't know if it'd be "tu misma" or "ti misma".

Answer 1

The answer as to why it is not ti can perhaps be gained from the entry in the dictionary of the RAE

1. pron. person. 2.ª pers. m. y f. sing. Forma que, precedida de preposición, designa a la persona a la que se dirige quien habla o escribe. Ya no trabajan para ti. Tenés que preocuparte más por ti.

2. pron. person. 2.ª pers. m. y f. sing. coloq. Designa a una persona

So you see from the first definition that ti would normally be preceded by a preposition. The etymology is from the Latin dative tibi which is usually translated into English as to or for you.

Answer 2

The answer key in your book would be correct if there weren't a comma after the name. Then the sentence would be a description of what Nora is doing:

Nora prueba este plato ella misma. | Nora tastes / is tasting this dish herself.

But you are right, with the comma included, the sentence becomes an order (imperative mood):

Nora, prueba este plato tú misma. | Nora, taste this dish yourself.

It would be less ambiguous with an exclamation point. That would make it super clear that an imperative is intended.

Now, how do we know when to use "tú misma" and when to use "ti misma"? Both are used to add emphasis. If the personal pronoun is a subject pronoun, use "tú misma." If it's an object pronoun, use "ti misma."

1. Subject. Example:

   Vas a tener que lavar los trastes tú misma. | You're going to have to wash the dishes yourself.

2. Object. Examples:

   Si quieres que valoren tu trabjao, debes empezar por respetarte a ti misma. | If you want others to value your work, you should start by respecting yourself.

   Trata de hacerlo por ti misma. | Try to do it by yourself.

Bottom line (simple rule of thumb): if there's a preposition, you need "ti misma." I put the prepositions in the examples in boldface to make them stand out.

Note: There are a few pronouns that happen to have the same form as subject and as object, for example "ella misma."