Newly solo cat

Hi all,

I have just recently lost one of my kitties (12 years) to a sudden
pulmonary embolism, and the other cat (Jane) doesn't really seem to
care that much. She is an exclusively indoor cat and reacts very
strongly when other cats are lurking around the house. Additionally,
when my other cat was alive, she would chase the now-deceased one a
lot -- I joked with my boyfriend that Jane thinks she's lost one of
her toy mice, not another cat.

However, Jane is definitely prone to boredom. She's quite the talker
and demands a lot of attention when we're home. I am wondering if I
should bring a new friend into the house or if Jane would just act
hostile toward him/her, as she does toward stranger cats outside the
house. Additionally, I favor adopting adult cats from the shelter
since they tend to get overlooked with all the cute kittens around.
But of course, if a kitten is warranted in these circumstances, I
would be happy to adopt one.

Some more background - now-deceased kitty was the reigning queen of
the household when Jane was adopted -- as a young adult -- but quickly
established dominance. So she's used to being "top cat," as it were.

Any suggestions would be welcomed!

Thanks,
kss