It sounds like your friend is excited about the news! From the message, it appears that Lisa's cat (or "Tatze" which is a term of endearment for a pet) has given birth to 3 kittens. So, you can congratulate her on the arrival of the three new little ones! Here’s a suggestion for how you might do that: "Herzlichen Glückwunsch zu den drei neuen Katzenbabys! Sie sehenreally süß aus. Ich freue mich so für dich und Lisa!" I hope this helps!