Based on the German text you provided, your friend is saying that Lisa's cat (referred to as "ihre Tatze" which means "her paw" in a cute/affectionate way) has had 3 kittens. The relevant part is: "Ihre Tatze hat 3 Junge bekommen" Which translates to: "Her cat has had 3 babies/young ones" So to congratulate your friend on her friend Lisa's new arrivals, you can say something like "Congratulations to Lisa on her cat's 3 new kittens!" or similar.