Well, you just have to pay 100 FG and reroll until you get her. Or her with someone(s) else. It will just cost 100 FG at the end. That's the magic of reroll gacha.

Now, IP wonder if we will get another reroll gacha for the .5 anniversary... Maybe I should keep Bluet and the others for their own 30FG gacha and focus on Water Poppy instead.