@Imseeh Jewelry is my absolute favourite! They have beautifully designed rings with incredible quality. If she's extra special go for a princess cut diamond ring, they're beautiful!
You will definitely find it at any gold shop in Souq El Dahab in Um Uthaina .. check places like @Sakkijha Jewelry @Imseeh Jewelry @Baqleh & Akkawi Jewelry
Hey! am not an expert but for 18k it costs JD 22.69 according to this Article http://jordan.freshgoldprice.com/en/, What I recomend is that you go to trusted places like @Imseeh Jewelry or @Shawkat Al Shami Fine Jewelry Salon and as the other tipster said bargain, bargain, bargain!