Based on the information provided in the message, it seems that your friend's cat (referred to as "Tatze") has given birth to 3 kittens/baby cats. The key information is: "Ihre Tatze hat 3 Junge bekommen" - which translates to "Her cat has had 3 young/babies". So in this case, you can congratulate your friend on the birth of her cat's 3 new kittens/baby cats.