Friend Has A Foot Fetish

So I never had a problem with this before but my friend from secondary school has a raging foot fetish. He always talked about what he got up to with some girls regarding it but this is the one time I have a problem.
I invited him to my house, my mum was there. My mum looks amazing for her age and often looks after her figure, she has shoulder length blonde hair, big boobs and a voluptuous figure but this put her in my friends sights. She was lying their in her nightie with her large smooth soles on her sofas armrest. Of course my friend was nearly slackjawed. He's a black guy so his boner was very visible but he sat down to hide it while I got us drinks but first I had to go to the toilet. I could hear them start talking as I left, I took about 25 minutes due to needing a shit but as I came out I heard the sound of squealing and laughing. As I peeked round the corner, my friend had my mums soles in his lap! He was lightly tickling them to which my mum just laughed and continued reading her book, then he went to soft rubs which made her moan loudly. Im embarrassed by my mums behavior and angry with my friend. Do you think she seemed to enjoy it and that he'll probably go for more?