The solution is to ask her, politely, directly, in private, for more interesting tasks. For all we know, the intern did exactly that. When I'm assigning tasks, then I'll often pick the person who is most interested in a given task, because it's safe to assume they'll be dedicated to it. Also note that "wanting to learn" is a good thing, and you should always tell your managers that you want to learn more.
You could ask by saying
"Hi JANE, I've been doing the same work here for a while. I would like to have some different development tasks, because I'm very keen on learning more about whatever you want to work on. Could I please be assigned some tasks involving that?
Tangental Thoughts For the OP
Your question as it is is a little confusing - you mention 6 developers, but only two of them are important - the intern, and yourself. Then a few sentences in you bring in the SCRUM master. I only mention this because if this question is indicative of your usual communication style, you will come across as confusing to talk to.
a case of fellow “female empowerment” or ... she doesn't perceive her as a threat...
I'm not sure what you're like, but when you start accusing people of discrimination - of any sort - without evidence, it makes you come off as potentially obnoxious. Again, if this question is indicative of your style at work then please, reconsider how you present yourself.
Of course nearly no knowledge is shared.
What have you tried? Possibly you have not tried anything - a good question to ask your manager would be how to encourage knowledge sharing. Give some thought-out options. Weekly meetings? Lunch-time sharing? Code reviews (for learning purposes)? You aren't just a coder, you're a human being - you're allowed to ask for a different management style or system to help you work better. That's what any manager wants from their staff!
Then you ask:
What should I do here? Directly confront her? Try to undermine her by some behind the scenes “politicking”, take it to our superiors or simply try to move to another team?
- Yes, but it's not a "confrontation". You're just asking for more interesting work. You're entirely entitled to do this, but you have to do it politely.
- Do not try to undermine her. Mostly because you're a junior engineer with possibly low social capital (who were you going to "politick" with?), so it's going to backfire. More generally, in this case there's no reason to undermine her. Please table this idea.
- You can and should raise it to your superiors, and I'm assuming she is your superior. If you actually have a different line-manager, do raise to them - again, politely, without "politicking" or accusation of discrimination, that you'd like more interesting work because you want to learn.
- You can move to a different team, but I'm not sure if that's the best solution. The core problem is that you seem to be unaware of how to interact in a team - that's ok, everyone learns this stuff over time. Moving to a new team will just mean you have the same things to learn, with different people.