[¯|_(ツ)_|¯]

Hey,

This is definitely a tough situation to be in!

You are only 13, and your cousin is 16. Both of you are in very different life stages so I worry that she is taking advantage of you. While sometimes an age gap is okay, in the US you'd even be at two very different levels of schooling and just are at different phases of life. Be careful how you proceed, because this may end up harming you more in the long run.

The fact that she is family is also concerning to me. It may make things difficult in the long run to do anything sexual such as masturbating with her. If you're caught it may damage the family dynamics.

You're also young. You're only 13 and have plenty of time to figure out sex and figure out girls. It's okay to take your time with it. The fact that you're unsure how you want to proceed is what raises a flag for me. If you're not entirely sure this is what you want it's probably a good idea to pump the brakes, so you don't do something you'll regret later on. Consent has to be given as an enthusiastic yes, and if you're unsure about things you don't have to give consent. I'd take some time to think about if this is what you really want to do.

I'd also talk to her about it and ask her to stop trying sexual things around you, at the very least until you figure out what you want to do. You don't need to be pressured or coerced into doing anything that you may not really want to do.

Are your parents open to talking about things like this with you? You said you don't know a lot about girl stuff, so maybe they can answer some of the basic questions you have. They may not get explicit with things but maybe they'd be willing to answer questions about dating, anatomy, and things of that nature. I'd also suggest that you tell them what your cousin is trying to do so they can set boundaries with her.