Hey, so I'm new here
I didn't really have anywhere else to turn to

First of all, I've been an emotional wreck for 4 months now. I've had problems with slight depression in the past but now I just have extreme mood swings, cry and overreact a lot and haven't slept well for 4 weeks. I'm generally not happy right now and feel extremely lonely.
I've had my best friend for about 5 years now. We always got along really well and I've never let anyone else get this close to me in my entire life. About 2 years ago we were in a relationship for 6 months and that's where the problems started. It was my first relationship so I was unsure about everything and I didn't feel save talking about anything that bothered me to her because she would always act like I'm unreasonable or get offended. She was also extremely jealous. Like, if I had to stay home from school because I was sick she got furious because I could be spending time with someone else in that extra freetime, but she had the same issue when I actually went to school. Long story short, I wanted to break up before she did but in the end she broke it off because she didn't like how shy I was or that I wanted to take things slow. After that we decided to stay best friends but I've had some romantic feelings for her since then so it's been difficult sometimes to be friends.
I also actually have a fear of interacting with strangers in general but it's worst with men. I get really scared and feel extremely uncomfortable and just want to leave whenever I'm expected to interact with one. It's because of my past...
My best friend knows this but now she wants me to meet her new boyfriend that she's had for 4 days. I told her I don't feel comfortable with seeing her with someone else yet and that I'm scared of not being her favorite person anymore and told her again how nervous men make me. I told her I couldn't just agree to it because it would mean that I willingly get into a situation that makes me really scared and uncomfortable. Her argument was that he is nice and that she would be there to protect me.
I told her it's not that easy and that I'm just really really scared but she completely ignores it, tells me I'm irrational and doesn't understand what my problem is.
I don't know what to do anymore, I told her exactly how I feel and why but she keeps saying that she doesn't understand and that she wants me to explain it to her. This is not the first time this has happened.
I want her to understand my feelings and just see it from my point of view but she constantly thinks that, just because something isn't a big deal to her, it shouldn't be a big deal for me either and that I'm just doing this to bother her or because I'm lazy.
How can I make her understand? If there is any way, I want to try because I can't take this anymore and if this keeps happening I will have to end our friendship because I'd rather have no one in life than someone who makes me feel like this...