Dave, answering you two questions..
Can she renew her stamp 4 now (3 months early) so we can go sort out the Spanish visa.
The max someone can renew his/her visa is 1 month. If you live in the country side talk to your local Immigration officer and you might be able to renew it little early as the Garda cards do not print anymore in the same Garda station and will not be handed over to you for at-least 3 weeks. Your local Immigration officer will stamp her passport but the Garda card would be printed in Dublin and will be sent to the concerned immigration officer and than would be handed over to you.
But if you live in Dublin, the Garda card would be handed to you on the same day of your renewal. Also you have mentioned that this is her third renewal so by law this time she should get a longer visa (Three years). By law spouse of Irish citizen's visa would be extended for 1 year, than 1 year and than 3 years and after three years she can apply for Irish passport and than HAPPY DAYS.....
Secondly, can we get the Spanish visa a few months early?
I would highly doubt that. Spanish visa would be issued only for few days, and depend on your flights, accommodation or holiday plan. Lets suppose you provide the below travel dates to Spanish Embassy.
For Example: From 5th July until 15th July. The visa could be issued to her from 3rd July until 18th July but if she already got schengen visa on two different occasions previously than she can apply for a longer schengen visa this time.
Hope my explanations would help you... All the best