Seamless underwear, cut higher on the hip than a regular pair, in your skin tone or the dress's color. That's the standard fix for visible lines under something fitted like Alexa.
Thong or Seamless Brief?
A thong removes back panty lines completely. If that's not for you, look for "seamless" or "laser cut," the edges are bonded instead of stitched, which is what actually shows through fabric.
Do You Need Shapewear?
Not necessarily. Light shapewear smooths, but it's a comfort choice, not a fix for a dress that doesn't fit right. If you need heavy compression to feel good, try sizing up first.
