Her passive allows for silent gunfire with any gun, making her a quasi stealth frame. Her other skill allows you to spot enemies on the minimap, to quickly target, or avoid enemies. She does not have a cloak / invisibility skill.
Personnally, Banshee is a good crowd control frame. Use her 4 on max reach and efficiency, and you can pretty much paralyse whole waves on defense and go afk while your teamates do the killing.
If you want stealth, go Loki or Ivara.