First off, why doesn't she care for Grandpa Longneck, despite possibly being related to him? She also may be a herd segregationist, and have taught Ali's herd to be that way. I kinda blame her for how Ali was for a lot of the fourth film.
Also, it seems so odd that Littlefoot would put down an elder like that, saying "I don't think the Old One is very wise.". Is he just being rude or is he dead on perhaps and we'll find out in the future? (The only other dinosaur that is quite elderly or that must be up in years was Doc, and that was in the TV Series and was when Doc was so mistrustful of Chomper that Littlefoot felt, rightly that that was hindering his friendship with Doc. However, once Doc accepts Chomper, Littlefoot actually apologizes for how he treated Doc and Doc says that Littlefoot was right to challenge him and they become pals again.)
However, the Old One almost kills Chomper in the TV Series. One might think she may have done that because he is a Sharptooth, but, consider this, despite losing his mother only a short time before, and knowing Chomper is the same species as the infamous Sharptooth that took his mother from him, it NEVER crosses Littlefoot's mind to kill Chomper, fearing he'd kill someone as an adult.
Also, if Ali returns in future films, the Old One likely will as well. What do you think of the Old One's behavior and seeming callousness?