Yes, your wife can accompany you to Spain without affecting your 90-day allowance, provided she holds a valid UK passport. As your spouse, she benefits from the EU's freedom of movement rights. This means she can travel with you within the Schengen Area for up to 90 days in any 180-day period without the days counting against her own allowance.
However, it's important to note that this exemption applies only when she is traveling with you. If she travels independently, she would be subject to the standard 90/180 rule applicable to UK passport holders post-Brexit.
To ensure smooth travel, it's advisable to carry documentation proving your relationship, such as a marriage certificate, especially if your wife doesn't have an EU family member residence card. While not always required, having this documentation can help clarify her status if questioned by border authorities
If you plan to stay in Spain for longer than 90 days, your wife would need to apply for a residence card as a family member of an EU citizen. This application should be submitted within three months of your arrival in Spain. Once issued, this card allows her to reside in Spain legally and facilitates travel within the EU.
For more detailed information on the application process and requirements, you can refer to the Spanish government's official guidelines on registering non-EU family members of EU citizens.
If you have further questions or need assistance with the application process, feel free to ask.