This is the correct translation:
Ihr war schwindlig.
She felt dizzy.
Almost all German statements have (and need to have) a subject. But there are some exceptions:
Sentences in passive voice:
Aktiv: Er hilft ihr.
Passiv: Ihr wird von ihm geholfen. Ihr wird geholfen.
In both passive sentences there is no subject in nominative case.
There are two kinds of passive voice:
- Vorgangspassiv
describes a procedure or event. Something will be changed.
Ihr wird geholfen.
Ihr wird schwindlig.
- Zustandspassiv
describes a state where nothing is changing.
Ihr ist schwindlig.
But passive voice can have a subject, and this even is the standard case:
- Vorgangspassiv
Sie wird beatmet.
Das Auto wird verkauft.
- Zustandspassiv
Das Auto ist verkauft.
It depends on the verb if you have to use dative or nominative case. Standard is nominative case. But helfen and some verbs that express a sensation can force the »subject« to turn into a dative object.
Ihr wird geholfen.
Ihr wird/ist übel.
Ihr wird/ist kalt.
Some people say, that in such cases the subject would be the word »es« that just has been omitted, but this is not correct. You can add an »es«, but even if it is in nominative case, it still is not the subject. It is a syntactic expletive.
- Ihr war ganz schwindlig.
- Es war ihr ganz schwindlig.
Sentence 2 is correct and has the same meaning as sentence 1, but you always can ask for the subject with »wer oder was?«. Let's give it a try:
Wer oder was war ganz schwindlig?
Wer oder was war ihr ganz schwindlig?
These questions makes no sense. It is the same kind of »es« that you can find in other sentences, even in such that have a subject:
Es fährt ein Zug nach nirgendwo.
Wer oder was fährt nach nirgendwo?
Here the answer is »ein Zug«, because it is the subject. You can not ask for this »es«.
Wer oder was fährt ein Zug nach nirgendwo?
This question is grammatically wrong, because it already contains what you are asking for.