Generally, keep her lower in your load order (especially after other custom-voiced follower mods) to ensure her appearance and voice scripts load correctly.
When she’s off the clock, you can usually find her hanging out in Belethor’s General Goods in Whiterun. A Few Tips for Your Load Order: Lily - Skyrim Messenger and Follower
is a fantastic mod that does double duty as both a fully-voiced courier replacer and a recruitable standalone follower. What makes Lilly special? Generally, keep her lower in your load order
She completely replaces the vanilla male courier with a custom-voiced female NPC. What makes Lilly special
Tired of the same old "I've been looking for you. Got something I'm supposed to deliver—your hands only" from that scrawny vanilla courier? It’s time for a change.
Do NOT set her home residence via other follower mods. If you do, she might get stuck there and you won't get your mail!.