Your friend mentioned that her cat recently gave birth to five kittens. So, you can congratulate her on the arrival of her five new kittens! Here's a message you could use: "Dear [Friend's Name], I was so thrilled to hear about the new additions to your family! Congratulations on the arrival of your five adorable kittens. It's a beautiful bundle of joy multiplied by five! I can only imagine the happiness and the exciting times ahead for you and your furry family. Wishing you all the best as you embark on this rewarding journey of raising your little ones. With love and joy, [Your Name]" Feel free to personalize the message further to make it more special for your friend.