Based on her message, your friend's cat, Lisa, has given birth to 3 kittens. So you can congratulate her on the arrival of the new litter. Here is an example of a congratulatory message: "Congratulations on the arrival of the adorable new kittens! Lisa's little ones look so precious. Enjoy this special time!" In German, you could say: "Herzlichen Glückwunsch zum Nachwuchs der süßen Kätzchen! Lisas Kleine sehen so bezaubernd aus. Genieße diese besondere Zeit!"