Ask Mr. Smarty Plants

In our Native Plant Database I did a COMBINATION SEARCH choosing "Nevada" from the Select State or Province option, "Shrub" from Habit (general appearance) and "Violet", "Purple", "Blue" and "Pink" from Bloom Characteristics–Bloom Color.  I did two more searches substituting "Subshrub" and "Herb" for "Shrub" in the search.  Unfortunately, I could find nothing that matched your description.  That, plus the fact that you describe it as a landscape plant, makes me believe that it is probably a non-native ornamental plant.  Our focus and expertise here at the Wildflower Center are with plants native to North America so we can't really identify or tell you too much about non-natives.  However, you can visit our Plant Identification page to find links to several plant identification forums that can help identify plants, both native and non-native.   If you have a photo, you can send it to one of these for identification.  Another possibility is to try contacting the Southern Area Master Gardener Program of the University of Nevada Cooperative Extension.  If it is a fairly common landscaping plant in Las Vegas, someone with the Master Gardener program is likely to know its name.