她的R舌头位置不是错，是one way of doing it.

看我的correspondence with her asssistant Tom:

Hi WQ,
I'm so glad you sent me this link! Great information in there. Would you mind asking this question on the Discussion Room Classroom? I think some other students would love learning from this. Rachel and I have talked a lot about the R sound. She teaches the R sound the way she does because it seems to be a little easier for some non-native speakers to learn. However, I will tell you, that as I worked on my speech in graduate school, we were taught to create our R sound the way you do. With the tongue tip pointing up, and curled back a bit. The hollow sound occurs when the tongue is pulled too far back, and you also don't want the tongue to make actual contact with the hard palate, because then you lose the sound altogether. But the way you make your R sound is fine! And we can talk a little bit about that during your session if you'd like! But please do post this link and question in the classroom for the rest of the students to enjoy and use, if you have time!! Thanks! - Tom

On Tue, May 14, 2013 at 3:17 PM, WQ