Lay it out flat and say “yes I’m spending time with my kid.”. Jealousy or not, you don’t have to change your relationship with your kid (unless you want to, but this isn’t a common thing to have to do).
As for the root issue, your partner either needs some hobbies to preoccupy her time, or the three of you can spend time together.
You should write a post sometime about what you know from the internals of Skype. I would read it.