Yes, she'll lose the lone parent allowance once you are co-habiting post marriage. However AFAIK she would get the benefit of it for 2007 to marriage.
For 2007 you are both over the cut-off of €34,000 for higher rate so no relief there.
Also for 2007 you will be taxed as single with reveiw of year of marriage after the year end. If the tax paid from date of marriage to end 2007 exceeds that which would have been paid on joint assessment there would be a refund of the excess. However note that this usually only gives anything back where there is some unuse of the lower standard rate cut-off of some other allowance/relief. As mentioned, you are already both above the SRCOP of €34,000. For 2008 you have the option of single / joint /separate assessment which you should look at the Revenue leaflets on.