No it isn't weird, many women are quiet during their orgasm.
When out I have noticed that women seem to check out other women more thoroughly than the men do.
Would I be correct in assuming women are more concerned about what other women think about the way they are dressed, opposed to what men may think?
It happened to me just the once. My girl friend and I were white water rafting, at the end of the day we visited the shower facilities. I had finished my shower and was waiting for her by the entrance. A girl, I don't recall seeing her earlier that weekend, walked out of the doorway straight up to me, threw her arms around my neck and passionately kissed me. I automatically responded returning the kiss. It was interrupted moments later by my girl friend, she came and loudly said "what the fuck". The girl pulled away, looked at my girlfriend pointed to an area within the camp site and said come join us, she walked away in that direction leaving us both speechless.
She wanted to spice things up, she is missing what she felt when younger. Her attempts to do so with you may not have accomplished what she was after so she gave up.
Sure talking can help, actions can speak louder though. She told you and showed you, what she wanted.
What have you done to spice up your marriage, what do you do for her so that she feels sexy and wanted. You might want to think about doing something before that guy at work or across the road does it for her first.
If the family friend is gay, or if he's not and you don't mind what might happen, or just don't care about his feelings, sure do as you please.
If you respect your boyfriend and the family friend then be considerate and don't tease.
What more does she have to do, wear a sign?