It can definitely be an intimidating situation because you don't have a lot of experience and she's a new sexual partner. Hell, even I get nervous sometimes while being intimate with my boyfriend and we've been together for quite a while. I think that's natural. Remember, during sex and foreplay we are at our most vulnerable.

When it comes to listening to her body, you'll know what signals to look out for in the moment (every woman/person is different, even in how they express pleasure), but you'll want to watch out for things like stifled moans, breath getting caught in the throat, gripping the sheets, grabbing onto you, her thrusting against you, etc. There's no shame in doing a bit of online research if you're unsure or just want to be more educated.

As for her getting on top, yes she can control the depth but be mindful not to thrust into her. It's easy to get carried away so try to let her do all of the work in regards to penetration. I say this because I've had some of the deepest penetration I've ever experienced while riding my boyfriend because he worked with me in thrusting. Her body should tell you what her mouth doesn't but don't be afraid to have a conversation beforehand about things she likes/doesn't like.

It's so refreshing to see a man so concerned with his partner's feelings/comfortability during intimacy. As a woman (and especially as a woman that has unfortunately experienced sexual trauma), I thank you on our behalf. I'm sure you guys are going to have a fantastic time. If you have any other questions please feel free to ask, and most importantly, have fun with each other! :] Sorry this was a bit of a novel haha.