My Japanese exchange partner cannot say "yeast" and "year" properly. She says "east" and "ear". She can hear the difference just fine and can distinguish "year"

My Japanese exchange partner cannot say "yeast" and "year" properly. She says "east" and "ear". She can hear the difference just fine and can distinguish "year" from "ear", even without context. I've spent 2 years off-and-on (it comes up every now and then) in an attempt to get her to say it properly. It's discouraging for her because she hasn't yet been able to do it. >(this can be easily disproven by an example of Japanese person who speaks English fluently, which clearly exist) All this proves is the individuals who can speak English fluently are capable. Not necessarily that others are also capable, thus this isn't a proof. I do agree they are physically capable of making the sound, but this argument isn't why and isn't convincing. Especially not to my teacher who maintains that others are capable but she is incapable. So this argument can also be considered potentially "harmful" for learners' self esteem and willingness to fall down 7 times, get up 8.