At the end of one of Eula's trailers, she seduces offers to dance with Amber. Also Eula's character 3 story has Amber running around Mondstadt and telling all the citizens about how kind and heroic Eula is to get them to not be afraid or hostile towards her. It's actually pretty sweet.
Also while I like the idea of a Lumine x Amber x Eula love triangle, this seems more like Eula being an overprotective big sister figure towards Amber than anything else. Her face is hilarious either way though.