Sew in/appliqué direction?!

Hi ladies! My dress has a small light stain on the front (hard to see but it still bothers me) and my seamstress recommended that if I’m not able to get it out,I have the option of covering it up with a sew in. I love my dress plain, but also kind of like the look of adding an embellishment. I don’t want the one in the example photos as I’d prefer not to have flowers on it. I’d prefer just rhinestones and/or a pearl combination. Should I consider doing it straight across my waist or diagonal on the hip to flow with the fabric? Or no appliqué at all? Thoughts appreciated!