Yes, you're right, in the meaning, I think "She likes the teacher" and "The teachers is pleasing her", are the same thing, in fine.
Why is it "ei" and not "eam"?
Eam would be the accusative. So this verb accept a complement in the dative I guess!
Edit: oh, I see, this verb is considered as intransitive. Now I understand!
As an intransitive, it cannot accept an accusative, but accepts a dative complement. The teacher pleases to her. So, it's like studere...