17M and 18F long-distance relationship — I can’t tell if this is my anxiety or real red flags

I’m 17M and my girlfriend is 18F. We’ve been dating for a couple of months, we’re in different countries, and we haven’t met in real life yet.

I struggle with trust and overthinking, and I’m trying hard to improve. I don’t want to accuse her of anything without proof, but there are some things that keep bothering me.

The biggest thing is her driving lessons. Every time she goes driving and comes back, she becomes very distant, tired, and has almost no energy to talk. She says it’s because driving with her brother is exhausting because he constantly yells at her while teaching her. We have argued over this and she said that whenever she will feel drained when she comes back from driving she will go to bed and we wont talk because it might lead to argument again if she talks to me dry. This has been happening for around 3 months, almost every time she drives.

I don’t want to accuse her brother or say something is happening, but my mind keeps wondering if her brother is being used as an excuse because the pattern is so consistent.

There have also been smaller things that make my trust issues worse, like explanations about accounts and emails. For example, she says she is okay with exchanging accounts but she makes excuses that she can’t give me her Discord because it’s connected to her school email and she doesn’t receive emails there, and also she said she wasn’t allowed to make Instagram with her own email so a friend helped her create it. These things could be true, but my anxiety focuses on them.

Another thing that bothers me is during arguments. When I ask questions, sometimes more details and reasons come out bit by bit instead of everything being explained at once. Sometimes she keeps saying risky things that if i reply without thinking out of anger then i will get in trouble and she keeps bringing such things up again and again and when i accidentally reply wrong to one of them then. She holds that and keeps saying that how much it triggered or hurt her, and suddenly the whole conversation becomes about what I did wrong instead of the original issue.

She has told me I’m being controlling before during a big argument but after the argument she said she likes that I care and worry. I know I have my own issues and I’m trying to trust her more. I’ve stopped questioning as much because I know I can’t control someone’s choices or ever have 100% certainty in a long-distance relationship.

I don’t want my fear to ruin something that means alot to me but i also don’t want to ignore literal red flags and stay like a clown.

But my biggest fear is cheating. The thought that someone could cheat while still loving their partner, acting normal, and never getting caught scares me more than anything. I don’t know if this is my anxiety creating scenarios or if I’m noticing real warning signs.
I’m not asking people to say she is cheating or that she is innocent. I want honest advice:

How do you know the difference between intuition and anxiety?
Am i making a normal situations sound bad?
How do you trust someone in a long-distance relationship when you can never have complete certainty?
What should I do when I feel suspicious but have no proof?
How do you notice red flags in my situation?