Hi, I know you want to do your best, but I think you are giving yourself too much grief. Firstly, there is not a mother or father in the world that would want to put her child into debt on their account. So, don't be worrying about getting a present as expensive as her posh friends. I'm quite sure what will make her day is the fact that you are happy for her to have found someone "good enough".
Talking of frames, TK Maxx in Blanch have some fab stuff. However, seeing as you are in Laois - Megapixels on JFL Ave in Portlaoise are doing unusual "framing" now. It's not actual framing per se. You give them a favourite photo and it's printed on canvas which is mounted on a square or rectangle timber frame, like a painting. So if you knew of a particular photo that she liked of herself and her intended, you could get that done.
Also, what I often do, is if I know where the person is going on honeymoon - in which case you do, I look that area up on the internet and book them a meal in a nice restaurant there plus a tour. So, not only is it paid for, but researched and organised and something to look forward to.