Well, this student of yours seems to have problems either with herself or with you.
1. She feels inferior to you, so by telling you that she preferred a different sight she tries to look important.(problems with herself)
2. She felt rejected somehow by you and tries to reject you back.(problems with you)
Why else would she tell you about it?
Or maybe she is just plain stupid? !
Anyway,none of these explanations have anything to do with the quality of your site or Eric's.
Your site is exceptionally good. My students are in love with your flashcards and your gamecards! I also find it good that you have started forums too.
Eric's site is fine too. I can't see any problem with your sites that would make her choose something else.
If she has such problems it must be hard to live with herself. You needn't be angry with her, says me.