I still don’t think she did it, but the more I think she should have taken the kid to France when I think about what is alleged to have happened. This is a riff on my previous post where I said:
Hell, thinking about it, she could have afforded to fly her and the kid over to Paris on the Concorde and stay at a 5 star hotel in the day for a naughty weekend (15 is the age of consent in France according to Code Penale, Article 227-25): why would she snog him in a parking lot?
Seriously, she could have been as outrageous as she is alleged to have been but have gotten away with it. Well, she would have to make it look as if they had a chance encounter to not run afoul of US law, but she could meet him at the Musée d’Orsay and steer him up to Gustave Courbet’s L’Origine du monde.
She could say something erudite about it such as: “the ample, sensual brushstrokes and the use of colour recall Venetian painting. I find his use of sepia tones quite masterful. Don’t you?”
Then, she could say “Tu peux me baiser si te veux…” She could explain that she meant he could kiss her if there are any untoward (or unwanted) assumptions which come from that request since the word “baiser” can be taken a couple of ways. This was a malentendu caused by her ignorance of the French language (Oh, I should have said “Tu peux m’embrasser si te veux…” silly me.).
Tant pis if he declined the propositions since she could head to a clothing optional beach where she would receive what would appear to be a red carpet greeting until she realised it was men’s tongues hanging out since she is a canon (super nana?).
She would also have the option of picking up a local if the kid rebuffed her offer as well. She could also have gone to Portugal (AOC is 14) or Spain (AOC is 13) if she was really intent on young talent.
If the kid had taken her up on her proposition and she brought her sprogs, the noises could be explained by her saying she was trying to get the proper French pronunciation of the number one. She was very happy when finally she got it right (un, un, un, un AHHHHHHHHH). 
Vive la France!
 An alternative explanation could be that they were discussing 20th Century music. The topic of authorship and female voices in electrovocal music came up. Ms. Shattuck was merely performing Berio’s Visage as an example of that genre. (Yes, although this piece was composed as a radio programme, it can also be performed as a stage work. It is the musical setting of a ‘drama’ that has never been written.)
Another option would be to say they were doing an impression of Jane Birkin and Serge Gainsbourg.