Unless they weren't able to book the actress, I kind of found it odd that his girlfriend Karen didn't appear to him as he was dying.
The actress is on another series, and unavailable.
The Karen character was not required, as each of the spirits of the departed were directly tied to people and experiences tied to or affected by his moral decisions, or who shared his view to some degree.
That was the purpose of Tyreese's journey--to settle his strength of morality once and for all (confirmation from the protagonist spirits) against those who embraced ends-justifies-the-means evil (Governor & Martin--and by an extent, others in his own group that slowly moved in that direction). Karen was not a part of that experience.
So, for Tyreese, the good people assuring him, taking him on the journey were--
Bob: Always looking toward hope after an initial negative world view, but ended up suffering thanks to Tyreese not killing Martin. Bob's spirit rejected that, since he was bitten (his mortal injury) at the food pantry, but Martin living meant he was able to help Gareth track the escapees, and ultimately, kidnap and cannibalize Bob's leg.
Mika: Right up to her end, she was like Tyreese--she did not want to kill others, it troubled her to even think of the act, even in theory. It is no wonder Tyreese was so supportive of her mindset while on the road.
Lizzie: In the grand scheme of things, she was disturbed beyond her control or understanding of death and the walkers, so I think her appearing to Tyreese suggests she was granted a reprieve, and is forever tied to her sister. Considering Tyreese's overwhelming desire for peace, that is exactly how he wished to see them.
Beth: Like her father, Beth believed in a higher purpose-- in the idea of good and faith (often expressed to Daryl) still existing / being the way to live. Tyreese was well aware of her beliefs (and his own views moving along those lines), so in watching her die--theoretically to end Dawn's reign of terror by triggering a
response (in others) without actually taking Dawn's life* seems like a sacrifice of the highest order to achieve peace. Tyreese did not want to see her die, but likely understood what she was doing, no matter how painful the result.
*Beth knew how to target
skulls of moving threats, some 2+ yeas into the ZA, so her stabbing to the shoulder cannot be an accident.