Hi Jeon...
Always apply... You've nothing to lose...
If your wife qualifies for Full Rate Carer's Allowance, you will lose the Dependant Relative componant of your Disability Allowance...
However, as the Dependant Relative part of you Disability Allowance is just €135.60 pw, and the Carer's Allowance is €2250.50pw, as a couple you'll still be better off by €84.90pw... And of course she'll have free travel in her own right too...
Best of luck with it all...
Darth...