It is a shame. I might have to watch The Wisdom of Friends (which I’ve never seen all the way through). Knowing Grandma Longneck has some focus might get me through it.
There isn't really much to see once you get past the opening scene with her. She has a couple of short scenes in between where she's looking for the kids with the other adults and then the ending when she finds them. The best showcase of her bond with Littlefoot is in the first five minutes, which is a shame. Throughout the series I'd say she stands out more in XIII, IV, and III, where she gets more equal screen time to Grandpa and both of them have more time with Littlefoot.
Another great opportunity ruined. If I were to remake that movie, I'd make some key changes. Actually, I don't know if I would remake that movie, but I'd probably transplant the opening scene which I actually kind of like and have it lead to a different plot.
I would also make some changes to that scene in particular. For example, I don't really like how reckless Littlefoot seems. He really should know better at this point. I remember having this idea for how it could play out:
* Littlefoot and Grandma are walking past some mostly dead trees, late autumn, ground is covered in frost. Littlefoot complains about not liking fall autumn because there isn't enough to eat, Grandma chuckles, says something old and wise about the seasons. Whatever.
* They find a tree with two remaining treestars left. "Look, there's one for each of us!" Littlefoot says.
* Grandma lifts Littlefoot so he can reach the two remaining treestars on the highest branch. Littlefoot eagerly snaps off and swallows his own treestar. But when it's time to grab Grandma's treestar, he drops it and the wind carries it away.
* Littlefoot is saddened but Grandma assures him it's alright - she wasn't that hungry anyway, and it's time to head back to the nest. They move on, but Littlefoot spots the grandma's treestar stuck in a bush on the other side of the ravine with the log. He decides to get it and surprise his grandmother, not realizing the danger.
From that point, the scene would play out mostly the same. But I think giving Littlefoot an unselfish motivation here makes his reckless behavior seem a little more understandable.