Reading your post I think that Miracle will be a very good choice , being an almost 100% floral. I can suggest you J'adore from Dior . Amarige is nice but is a stong perfume your mother must like tuberose or other stong smelling flowers to enjoy it. You can try also Verry Irresitible ( roses but soft) from Givenchy.
Or a nice and soft whispering floral with good staying power: Cartier de Lune being somehow quit close to Pret a Porter
Hope that all these will be useful to you