@ambitiouspoetry This has more to do with proportional arm length and previous upper body training than anything else.
If your arms are longer for your body, you'll have more issue. If, like many women, you have never trained upper body, you'll have more issues (less muscle mass/ lb, less muscle memory, and less familiarity with movement patterns).
If I'm going to be honest, I'm not sure there has been a time in my life where I couldn't do a pull-up. My arms are a little long for my body, but I'm 5 ft tall, so it amounts to an extra inch on each side, which is nothing. I did gymnastics on and off as a kid, and am upper body dominant naturally. When I decided to start working on them 2.5-3ish years ago, I used the neutral grip (the only one that is not really wide for a small person) on the assisted pull-up machine, with about 10-15 lbs of assistance. After a month, I decided to try them on my own, and had no issue getting several chest to bars (which is just what I always thought a pull-up was).
On the other hand, my favorite gym buddy, who is at least as strong as me, and puts up way more weight than I do on overhead squats, cleans, and jerks, has been struggling with them for a year. Her arms are long, and she doesn't have the base training though, so she's starting from scratch.
Bottom line: You might have to train your butt off, but you CAN and WILL get them if you work hard. There just really isn't a standard time frame.