Does she need a visa? We will be traveling together.
If your wife's residence card notes that it is the residence card of the family member of an EEA national, then she can travel with you in the EU without needing a visa. If the residence card does not have this notation (for example, if she acquired her residence through employment, or through essentially any avenue other than being your wife), then Spain can require her to have a visa, and, more importantly, the airline won't let her board without one.
Residence cards with the required notation are sometimes called Article 10 cards, after the relevant article in the freedom of movement directive, 2004/38/EC.
In that case, what kind of visa?
If your wife doesn't have an article 10 card, then she should apply for a Schengen short-stay visa using the normal form. The visa should be considered using an accelerated procedure, and the grounds for refusal of the visa are limited. In particular, it is not necessary to prove financial means.
Accordingly, the application form indicates that several questions are not to be answered by those applying as family members of EU or EEA citizens, and she should obviously ignore those questions.