"No es culpa mía (de) que ..."

Question

On spanish.about.com they explain that you would use "que" if you can replace the English "that" with "which" and it would still make sense. So, it's a pronoun.

El plan que quiere es caro. (The plan that/which he wants is expensive.)

You would use "de que" in any other case. It's then a conjunction.

El plan de que los estudiantes participen en las actividades es caro. (The plan that/which students participate in the activities is expensive.)

In another post on this site, the most upvoted answers says:

You need to replace "que" and everything after it with "eso" (which means "it"), then you will easily see which one is wrong.

I've seen a couple of examples, however, where I was confused that they sometimes used "que" and sometimes "de que" although I can't see that the above rule would be applicable.

I only have one example present right now, which is taken from spanishdict.com:

No es culpa mía que estés enamorada de mi.

Applying the first rule above, the proper translation into English would be "that" as a conjunction. Using "which" is just wrong.

It's not my fault that/which you're in love with me.

According to that first rule, "de que" would be correct and, hence, the example given were wrong.

Considering the second rule, there's already an "it" in the sentence. Attaching another "it" would be just wrong anyway:

*No es culpa mía (de) eso.
*It's not my fault (of) it.

Eso no es culpa mía.
It is not my fault.

So, if I applied that second rule rightly, the use of "que" were correct.

That raises the following questions:

1. Which of the two rules cannot applied to this example? Which rule is 'incomplete', that is? (If I'm not mistaken, the first rules dismisses "que" as a conjunction altogether.)
2. Assuming that the "less good rule" is still generally true, how would you extend the rule to cover that case?
3. What's correct in this very sentence anyway?

Answer 1

I would say that your rules are good rules of thumb, but none could be declared an "ultimate" rule, since those are the "English" version for the Spanish dequeísmo phenomenon.

In

No es culpa mía que estés enamorada de mi.

the "que" is introducing a subordinate sentence with a subject.

No es culpa mía que (tú) estés enamorada de mi.

When the "que" is introducing one of these subordinate substantive sentences you don't use "de que". The subject of a sentence is never preceded by a preposition. The second rule is incomplete. Is not enough that the "que" is a conjunction. It depends also on the sentence that is being introduced via the conjunction, or even the verb used in the first sentence.

So the correct version of that sentence is

No es culpa mía que estés enamorada de mi. (no preposition de)

Best rules, of course are the ones given by the language, since translating to another may not always do the trick. It doesn't just have to do with "that" or "with". If you check the link you'll see that it has to do also with the verb (some pronominal verbs would require the preposition de in situations other verbs would not, such as alegrarse or preocuparse. Other times it depends on a certain preposition that used with a given verb, such as "fijarse en que..." ).

Me alegro de que estés bien

Pienso que está bien (nunca Pienso de que está bien)

Cuida de que mis plantas no se sequen (since you use the preposition "de" with cuidar: Cuidar de un niño)

The RAE's rule of thumb is actually different to the ones you provide (it is also available in the link, third point). They suggest to turn the sentence into a interrogative one. If the question needs to start with the preposition de then you will use the "de que" construction instead of just "que".

Qué no es culpa mía? No es culpa mia que estés enamorada de mi.

You would not ask

De qué es culpa mía?

De qué se alegra? --> Se alegra de que estés bien (you would never ask "qué se alegra")

Qué piensa? --> Piensa que ... (you would never ask "De qué piensa"?)

Qué plan quiere? (no "De qué plan quiere") -->El plan que quiere es caro.