Is it normal my gf got her friend to give me paizuri?

My girlfriend knows that i really like girls with large breasts. her's are average but she has plenty of other charms and i love her a lot. she's even talked about getting implants just to please me, it kind of sounded like she was joking, and i really do hope she was. i told her never to get implants because real small ones are way better than fake big ones. anyway, so she invited this new friend over and she was stacked! it was incredible! but not as incredible as my GF telling her to give me a paizuri. i was shocked, i was like "are you serious" and my GF said she knows that this is something she can never do to please me, so she got the next best thing. her friend was cool with it too, saying she would do this as long as it was always okay with both me and my GF. But is this normal, for a girl to go as so far as to let someone else pleasure her boyfriend? even if it is just with their breasts?