They are confused

You keep watching in silence until the grand warmother finishes feeding. When she does, she lets go of the servant she was draining and it drops to the floor. The warmother looks at you and asks “Sabine? What’s happening?”
“It is the Burning Rose’s will.” You lie.
“Her will?” The warmother asks? She points at the dead servant on the ground and says “You mean to tell me this is what the Burning Rose wants?”
“I know.” You say. “It doesn’t look like what the Burning Rose would want. But if you can gather all the sisters to the dining hall, I will explain everything to everyone.”
The warmother raises one eyebrow. She obviously has trouble believing you.
“But right now you have to find any remaining servants and prevent them from leaving the high abbey. Imagine any of them get out and start spreading news of what happened here tonight.”
“Very well.” The war mother says as she walks out of her office. “I will have the servants rounded up and the sisters gathered. But you had best come up with a satisfying explanation.”
When the warmother exits the door she turns back and says “Oh Sabine, find something to wear. You do not look presentable.”
You look over your body and remember leaving your room without any clothes on your person. You look around for something to cover yourself and discover a black cloak among the warmother’s possessions.

Sometime later you find yourself in the dining room. It is filled with sisters of the Burning Rose, all of them vampiresses. They are talking about what happened earlier. Most of them are nervous and scared, a few of them are crying. You are standing in their midst, wearing nothing but a black cloak.
You get up on one of the tables and speak to them.
“My fellow sisters. I am Sabine St. Croix, a sister from White Cliff abbey, and I bring sad tidings. The abbey’s wards have failed and it is overrun by daemons.”
“Oh goddess. Sister Angela said. “It’s one horrible thing after another.”
She is one of those that is crying. Hanna quickly hugs her and tries to comfort her friend.
“What happened at White Abbey is indeed a horrible thing.” You say. “But what happened to us this night is not.”
And just like that, you’ve got everybody’s undivided attention.
“Just after the sun went down, I received a vision from the Burning Rose. She told me she is furious about what happened at White Abbey and she wants the daemons to pay for what they are doing to our sisters. But she also knows these daemons are dangerous and many of us would fall to them if we were to simply attack them. That is why she made a pact with the Winter Lotus.”
Several of the sisters gasped upon hear the name of the goddess of frost and vampirism. For a moment, you are worried they might realise you are lieing to them, but you're too far now. If theya re to believe you, you need to keep the lie going.
“Because of this union of two goddesses, all of us have been granted extra ability’s. We can now fight daemons all night long and not get tired. We can wage a war on all of daemon-kind for centuries, for we no longer grow older. A wound that would have been fatal yesterday can now be healed, without leaving any scars.”
When you are explaining this, you are moving your arms around you so much, you’re afraid it would cause the cloak to open up too much and reveal your naked body to the entire sisterhood.
“We have been transformed into something greater. A stronger more powerful sisterhood which will be the bane of daemons everywhere.”
“That may be, but it also transformed us into murderers.” Hanna spoke up, still cradling Angela in her arms.
“Only when we fall victim to ‘the thirst’.” You quickly reply. “It is entirely possible to feed on a person without claiming their life.”
You motioned to Leanne and Jola. You had spoken to the twins before your speech and instructed them to bring you one of the surviving servant girls when you give them the sign.
They did as you had asked them and bring you a human. The girl is kicking and screaming, trying to get loose and run away, but two vampiresses are too strong for her.
They get onto the tables with their captive and have her face you. You look into the servant’s eyes, your eyes turn red and you say “Accept the Winter Lotus.”
The servant stops struggling and repeats “Accept.”
You motion the twins to let go of their captive, which they do. When released, the woman no longer tries to run away.
“Dear servant.” You say. “I’m sorry for asking this, but I have not yet fed this evening. Would you mind if I have a taste of you?”
“Not at all, sister.” The servant politely replies. She rolls up her sleeve and offers you her arm. “Please take as much as you need.”
You take her arm and sink your fangs into her biceps. You drink what you need, then let go of her.
“Thank you.” You tell the servant. “You have a lovely taste.”

You then turn back to the crowd. Some of the onlookers have their fangs half extended just by watching.
“As you see, there is no need for ****. You can take all you need to pass one day from one person without killing them. Just don’t feed on them four times in a row, grant them some time to replenish the blood they’ve lost and they should be fine. Just get a couple of humans, use the eyes on the Winter Lotus on them to make them your thralls and feed on a different one each day.”

All right, this is the best you could think of. You hope it is enough to convince them.