Lilith's fear waned upon hearing how Vincent accepted Sakura to become his woman. Sakura was now a woman Lilith was going to share her man with, and as Vincent told Lilith before, he asked her to treat each other like sisters and have each other's back.
It was to stay together as a family even when the world is against them because of the mark on their bodies that doesn't even go when the skin gets removed or melted. Vincent's mark remained visible after the Royal Guard Ant's fight. Thus, the retainer mark could as well.
Lilith saw Sakura in a different light, and she felt more of a reassuring person than a scary one now.
However, Iris and Lupa didn't approach to congratulate and welcome Sakura into their increasing family.
Iris kept her distance, yet a smile with a pair of cute dimples was on her face. Iris didn't look like she was afraid nor disliked Sakura. But she was still shy to talk to a person she barely said a word to.