what worries me is she keeps stuff bottled up real tight.
I know that reaction, internalizing your pain, grief, and all of the tumultuous emotions and nagging doubts that are afflicting you, is pretty common, and I would probably feel the same way, were I placed in her position.
The tendency is to withdraw from the things that are piercing your soul, and to insulate yourself from a scenario that was once inconceivable, but which is now a manifest reality.
That's an instinctual reaction.
Fight or flight.
There's really nothing that she can do to fight the mortality of other people she loves, so the natural response is to find some sort of mental sanctuary in which to cocoon herself.