In a very soft-science world, in a lush forest far away from civilization and their laws, especially the one about squares and cubes, lives a young, female drider. One day, while hunting for dire-boar at the far end of her territory, she meets a handsome young male of her species. He proves to be witty and charming, as well as a hunter almost as good as she is. Together they spend the evening having a feast, which turns into a night of romance. Not too much later she finds that her appetite is increasing and her abdomen feels strangely full... There's only one conclusion - she's pregnant!
This character's world is decidedly soft on science. There is a lot of magic that works just because it would be fun if it did. However, for our spider heroine I'm trying to stick very close to the feel of her being a spider, only scaled up. For example, if she goes too deeply underwater her spider body's book lungs will not work. Since her human lungs do not provide enough oxygen on their own she'll grow short of breath and eventually drown if she doesn't get out. Her legs also work using the hydrostatic pressure of her 'blood', meaning she has to rest every so often to rebuild pressure. She also needs to capture big prey to satisfy the enormous energy requirements of her metabolism.
In case it is relevant, her spider body is based on the Antilles pinktoe tarantula. She is also a young and healthy individual, living a lone hunter-gatherer lifestyle.
A drider is essentially a spider with a human torso in place of the head. They are sometimes known as 'spider-taurs'.
Example image: Source: DeviantArt, image by FluffyXai
In our reality her spider species apparently produces clutches of at least dozens up to a few hundred eggs. While it would definitely be a lot of fun to write about a spider family taking over and webbing up the entire forest, that would derail the current direction of the story. I would like to keep the feel of 'spiders lay a lot of eggs', without having to introduce dozens of new characters.
This is why I'm looking for a justification for having her produce about 7 to 12 eggs.
I would prefer to avoid having the eggs and/or hatchlings die, to keep the tone of the story lighthearted. I would also prefer a biology-based answer over a magic-based one, since for the latter I would then have to justify why the magic works that way.
In case this bears repeating, I am aware that a drider (or any human sized spider) simply cannot exist based on the laws of nature of our world and that is not what this question is about.
Why am I looking for a justification when a simple 'it just works that way' would probably do? Because misaimed realism in fantasy stories is fun, of course!