Why not get both kittens? I know u are worried about Boo but she might love having more kittens.
I had 2 cats - Sunniday and Zebra then had to put Sunniday to sleep due to Chronic Renal Failure so I was worried about Zebra being alone during the day then a friend found out her vet had 2 kittens who needed a home. I only wanted to own TWO cats since I live in a SMALL basement apartment but when I went to look at the kittens, I fell in love with both and the vet said she didn't want the brothers separated. I ended up bringing both home and guess what??
This is VERY UNUSUAL but Zebra IMMEDIATELY accepted them both! She treated them like her own babies!!! Now the boys (Spike and Buddy)are 1 year old and they just ADORE each other! Often Zebra and the boys would wrestle or chase each other around for fun.
I have just adopted a 4th kitten named Pepper(NO MORE than 4 CATS since I live in a SMALL apt as I said before! Grin). I've decided to adopt the 4th kitten because sometimes the boys would be chasing each other and Zebra looked kinda left out so I thought the 4th kitten would be good for Zebra and it looks like it so far!
The boys aren't sure yet of Pepper but Zebra ADORES Pepper and Pepper ADORES Zebra...
So go ahead and get both kittens!
And this way you'd have more choices of who to cuddle or play with- if one cat isn't in the mood to be cuddled or play with, you'd have 2 more choices to try to cuddle with! Heheh.