I never really saw the scene "for the first time", because the first time I heart the story of the first film was when I was reading an illustrated storybook of it together with my grandfather. I remember that I didn't say a word. I was just sitting there, looking at the picture of the dying brontosaurus in the book and asking myself things like: Is this really happening? and What's the point of this?
I'm really surprised of how good I can remember the text that my grandfather was reading out loud for me back then. At this sentence (rough transition from what I can remember):
"Mother, please keep talking to me!", but his mother didn't answer. She had died.my grandfather lowered his voice in a sad manner and looked at me as if he wanted to make sure that I was okay and that I was able to understand what had happened. Then he turned the page.
I have to point out that the death wasn't as sad for me as for the people who saw Littlefoot for the first time in the original movie, simply because I grew up with the sequels. I knew that Littlefoot would be fine in the end. I knew that Littlefoot wasn't completely alone, because he was going to make the best friends he could ever ask for.
I think the most efficient method to make a true land before time fan interested in a sequel like 5, 9 or 14 is just to say that Littlefoot's mother is mentioned again. I've already seen that in reviews on websites that sell those movies. For me the moments when she is mentioned again are some of the most emotional and memorable of the whole series, so I would definitely love to see more of them.
I wonder how others see her?
The short screen time she had her and natural behaviour leave room for many different interpretations of her character. I found many different versions of her: ( this might a bit long so I'll put behind "spoiler")
How the people who own this book which came out before the film might see her:

How we saw her in the film

How some people who grew up with the sequels might see her:

How I saw her as a young child:


If you are interested in other character interpretations of her I would highly recommend to watch the first film in other languages. I think her character is more orientated on a real dinosaur than on other cartoon characters, so her personality isn't defined by movement. That's why her character can change slightly with her voice actor. I can't speak for all version, but I've noticed that Helen Shaver sounds more quiet than the German voice actor of her for example.