You should read the link @Gilthoniel provided in one of the above posts. I'll quote from that article:
"Yennefer can hear thoughts. When she first met Geralt, he looked her over and realized she used to be a hunchback. He made a game in his mind of trying to decide what deformity she used to have – since most sorceresses have a deformity. Yennefer heard his thoughts, and in anger, she enscorelled him and used him to get revenge on everyone who had been unkind to her in the city. She had him go around spanking people for calling her names and putting her down, then later she tried to get him out of prison when he was arrested. She even tried to send him through a portal so he would be safe when the djiin took over the town.
Yennefer pranked Geralt to get back at him for silently mocking her about something that she is very sensitive about. It’s revealed in the last novel that she hated being a hunchback so much that she tried to kill herself when she was a girl. "
And of course, she also helped Dandelion, who otherwise would never have sung again.
Of course. She helped Dandelion (because at that time she thought still controlled the djinni) and then mind controlled Geralt and nearly got him killed before he wound up chained to a dungeon wall (ha ha, funny prank) all because he looked at her and realized she used to be a hunchback. It was obviously true love at first sight.
Thanks, it all makes sense now.