The problem is that they would blend any signs of Littlefoot having not overcome his mother's dead in the movie. What does "overcome" mean in this case anyway?
If "overcome" is to say that Littlefoot managed to deal with his grief so as to live on happily and not brood on his mother's fate all the time, then I would definitely agree that he came over it. He had his grieving time in the original movie and we don't see any really mournful moments caused by his mother's fate in the sequels.
She wasn't mentioned at all until LBT 5 where there were a few lines refering to her in the song Always There. Next time she was mentioned was in LBT 9 (where Littlefoot wished she had given him a brother and where a cloud shaped like her appeared in the sky), and finally there was a short mention of her and her fate in LBT 10.
This does not mean however that there are no such moments at all though their existence can neither be proven nor disproven so it is up to us to deceide what we want to think. There are some hints though which we might want to take into account when deciding how Littlefoot is probably dealing with his mother's fate:
I remember now
like it was yesterday
she would hold me close
and then I'd hear her say
You know I'll never leave you
You can find me everywhere
in the morning light and evening star
I'm always there
If these were the words of Littlefoot's mother I don't expect he will ever look into the morning light or watch the evening star without remembering his mother. This memory need not depress him. On the contrary he may even find that thought encouraging.
My interpretation is that Littlefoot is definitely still thinking about his mom. The death of a parent is far too important an event for a sensitive character like Littlefoot to just forget about it. He does not allow her fate to drag him down though. His mum died when she tried to save him. She "contacted" him even after her death to make him go on and find the Great Valley. Perhaps Littlefoot wants to live as good a life as he can to make his mother's sacrifice worthwhile (though I doubt he would spell out the thought like that).
Perhaps there is even a kind of "spiritual contact" such as the one we saw in the original movie (or probably one less direct). I've included a reference to Littlefoot's mother and some kind of contact in every land before time story I have written so far though that contact changed from a very explicit one (in the first story I ever wrote she more or less tells Littlefoot what to do in a dream) to a more subtle kind of contact. In my current story I let Littlefoot describe it like this:
“No, please stay. I don’t hear her anymore anyway. Already for quite a while, but I hoped I would hear her again.”
“Your mother?” asked Ducky quietly and Littlefoot nodded silently.
“You can hear her? What did she say?” asked Cera and a short moment later she added: “Or don’t you want to talk about it?”
“It is not as if she would speak and say do this or do that. It’s more that I feel her presence the same way I felt it during our journey to the Great Valley.” Littlefoot fetched deep breath. “Since then I felt it only very rarely and whenever I felt it something important happened shortly after. Good things sometimes and sometimes bad.”
“You believe something will happen, Littlefoot?” asked Petrie. Littlefoot smiled helpless and shrugged: “Maybe; at all events it has always been the case after I felt my mother so far.”
Apart from the morning light and evening star implication the presence of a cloud image of his mother in LBT 9 might indicate that there is still some kind of contact, but then again cloud images have been used so inflationary in LBT 10 (and possibly comparable "rock images" in LBT 6) that maybe the significance of a cloud image should not be overrated.
And on this topic, isn't it also a bit strange that Littlefoot is willing to take care of Chomper almost right away? I mean he may have been just a baby, but he was still a member of the same race that killed his mother.
I strongly agree that this is a rather confusing aspect of LBT 2. The movie seems to start right after the end of the original movie (the song Peaceful Valley) suggests that no long time (possibly a few days) has passed since their arrival in the Great Valley and the fight with the Sharptooth. It is strange that Littlefoot of all was the one to adopt Chomper. Maybe Ducky would have been a more plausible choice.
I've often wondered whether or not Littlefoot ever told Chomper about his mother's fate.
As for playing Sharptooth attack it is kind of like our playing tag, so perhaps Littlefoot may not think too much about it. Human kids who lost a dear relative in war may well continue to play "war games" on the computer or with friends. I'm not sure if this can really be compared, but there is probably no unimpeachable explanation for Littlefoot's willingness to play sharptooth attack and adopt Chomper.
Perhaps Littlefoot really sees the death of his mother as part of the circle of life and will therefore not condemn sharpteeth in general. Supporters of the theory that revenge was a main motive for Littlefoot to kill the original movie's Sharptooth may assume that any possible hatred for Sharpteeth as a species died along with the sharptooth who killed his mother. People who don't assume revenge was a central point in Littlefoot's decision to get rid of the sharptooth (that includes me) may see the very lack of revengefulness (at least of that degree that determines actions over common sense) as a point which may help to explain his "open-mindedness" about Sharpteeth.