What’s the expected behaviour from men when flirting through WhatsApp?

TL;DR: How to text a girl and take the texting to another level without making her loose interest in me or acting weird.

So I (male 26) have asperger and social interaction is kinda hard to grasp for me. So I’ve never had success when flirting with a girl. I don’t know how should I act, what type of messages should I send nor how often should I send messages.

I oftentimes get worry about looking too desperate if I start to send messages on a daily basis or through out the day as well as if she sends me photos should I compliment her or compliment something else about the photo like the background or something like that.

I’ve read so many books and blogs about this and they always say something like act like you don’t care about her, to don’t respond after some time, hours or even days, and stuff like that, I guess you know what I mean, basically to be a jerk, but this has only lead me to the girl loosing interest in me. But if I try the opposite, being more attentive and all, she also looses interest. As well as when I try to be in the middle, sometimes being attentive and some others acting like I don’t care too much and giving her her time, but at the end they also loose interest and it leads me to nothing.

Lately, I met this girl (female 25), I was kind of attentive and she was kind of responsive to my approaches, nevertheless at the end someone else make out with her and I stopped treating her the same way to only treat her as another male friend as well as not texting her at all. After a couple of weeks she started to texting me for no reason and her attitude was a complete turn from the usual. I’m afraid she’s only missing my attention and she’s only teasing me, I thought I was already over it, but the time she showed me her sweat side my brain got very confused.

We’ve been texting each other daily, mostly in the evening after work. She sent me some photos of her face but with a sexy look, she’s been telling me she misses me and that she wants to see me again.

For context, when I met her she was kinda weird, not very talkative, not only with me but with everyone, she sometimes hugged me and told me that I was good looking, but whenever I try something like touching her hand, for example, she would back off. We live on the opposite sides of the country but there’s a chance of meeting again because of my job and she knows that.

Please help