Emilia has feelings for Subaru. Obviously this is the case. But Emilia doesn’t really understand romance, or romantic feelings. At heart, she’s a young and naive girl, in many ways. She cares about Subaru a great deal, but she herself cannot recognize these feelings as necessarily being “romantic love,” and Subaru himself is fine with this (mostly). Until Emilia herself can emotionally mature, she won’t be able to return Subaru’s affection in the way that he desires, but given how she clearly feels – I doubt it will take forever.