Read other letters about this article
There is a huge issue here that the letter writer never seems to fully (or partially) process: How/will she fit into the nuclear families that she intends to use (help?) to satisfy what appears to be a life crisis.
The "helpful aunt" is a nice notion in the abstract, but these families may not want her involvement at the level she seems to intend. I can say as a parent that I wouldn't. This is especially true given the fact that she seems to be approaching her nieces and nephews as more of a "fix my life and fill an emotional void" project than anything else. I can see their are altruistic motives as well, but there is a real danger that she will be an intrusive burden to these families and friction will develop.
If kids are the answer, then have your own kids and they can interact and grow with their cousins. If you don't want to pursue that role, then attaching yourself as a quasi-parent to the other families will be only a temporary solution to your life crisis, a complete failure, or both.