Shruti
This kannadiga actress has acted in few couple of movies in Malayalam like oral matram, swantham Malavika, CI Mahadevan 5 Adi 4 inch etc. However she was known for her portrayal as Dr. Ambili in Kottaram veetile apputten opposite Jayaram.
Sudha Rani
This Karnataka state award winning actress has acted only in one movie opposite Jayaram in Adythekanmani. This movie was a big blockbuster and remade into Hindi as beti number 1. The actress was loved by Malayalee audiences for her natural beauty and good acting skills. But we Malayalees were not lucky to have her back in Malayalam movies.
Sumalatha
There is no introduction needed for sumalatha in Mollywood. She has acted in multiple Malayalam movies and wooed the audiences with her acting and natural beauty. Her most popular character was Clara from thoovanthumbikal. Her pairing with superstars Mohanlal & Mammooty was always appreciated by the audience.
Madhoo Shah
Madhoo or Madhubala is technically not a kannadiga as she is from a Tamil family but ever since her comeback she has been part of sandalwood industry with good characters. Madhoo has acted in movies like Yoddha, Nilgiri, Ottayalpattalam, Ennod Ishtam koodamo. All these movies were blockbusters of the time. Her pairing with Mukesh is one of my personal favourite onscreen couples of Mollywood.
Nikki Galrani
Nikki has played multiple movies in Malayalam. Her most popular movie was Vellimoonga. She is quite perfect for playing Christian characters in Malayalam movies. Nikki herself accepted that she is loved a lot by Malayalee audiences.
Soundarya
Soundarya has acted in two Malayalam movies. Had she been alive she would have been doing many Malayalam movies as she was quite perfect to play a natural Malayalee women onscreen.
Sanjana Galrani
Sister of Nikki Galrani has acted in movies like The king & commissioner, Casanova etc. However unlike her sister Sanjana was unnoticed by the audience as the movies she has acted was not a big commercial hits.
Vedika Kumar
Vedika has acted in movies like Sringaravelan, Cousins, James and Alice, Welcome to Central Jail etc. her most popular roles was that Alice from James and Alice.
Madhavi
Madhavi though born in a Telugu family has made a name of her own in both Kannada and Malayalam movie industry. Her most famous role is from Akashadhoothu where she played a single parent who is a blood cancer patient who wanted to keep her children safe before her death.
Parul Yadav
Parul though is a North Indian, she is a popular actress in sandalwood industry now; she started her film career from Malayalam. Her debut movie was Krithyam opposite Prithviraj. She also acted in a crime thriller Black Dalia. She didn’t became a popular actress in Malayalam as the movies she acted were flops.
Shraddha Srinath
This Kannada Filmfare winning actress started her film career from Malayalam. Her debut was a Malayalam movie named Kohinoor. She played a parallel lead in this movie. This movie was a flop.
Vinaya Prasad
Vinaya has acted in multiple Malayalam movies in her career. She is popularly known as Sridevi from Manichitrathazhu. She also played lead roles in Malayalam TV industry. She still acts in Malayalam movies as supporting actress.
Meghna Raj
Meghna raj has acted in multiple Malayalam movies of which most popular characters of her are from the movies Beautiful & Memories.
Veteran actresses like Bharati, Jayanti etc has acted in multiple Malayalam movies.
Now actresses who have acted in sandalwood industry from Malayalam:
Sitara
Sitara has acted only in Kannada movies continually for 7 years and has been part of good movies.
Bhavana
Bhavana is another malayee actress who had made her own name in sandalwood industry.
Nitya Menon
Nitya though her parents are malayees she has been born and bought up in Bangalore. She has done few good movies in Kannada.
Actresses like Parvathy Thiruvottu, Prayaga Martin, Chippy, Navya Nair, Gopika, Divya Unni, Nayantara, Meera Jasmine, Mamta Mohandas, Vani Vishwanath, Vijaya Lakshmi has acted in Kannada movies.
Kannada actors like Ananth Nag, Vishnuvardhanan, Ambareesh has acted in Malayalam movies which is mentioned by others so I am not repeating here. Mohanlal & Mammooty too acted in Kannada movies.