I love
Althea. You could use the nickname
Thea, or no nickname at all. It's a great name.
I'm not a fan of your middle names though. They all seem like filler names to me. I like the idea of honoring your mother. How about:
Althea Kitty Althea KariAlthea KajaAlthea CadiAlthea KatinkaAlthea Karin
Or away from the
Kate theme:
Althea LiliasAlthea MarnieAlthea Rosie Althea Maddie
Mommy to
Myrtle Nola (22-10-2012) and baby due 25-05-2015