yrangd, I've been there and hope what worked for me will work for you. When I was a 23-year-old woman, I applied for a wildland fire hotshot crew and was accepted. The acceptance package told me the fitness criteria I would need to meet on day 1 in order to be on the crew. All of the crew, men and women, were expected to meet the same criteria. One of the criteria was to do 7 pull-ups. I thought I was in decent shape from working outside all the time, but like you, I couldn't even do one. There was no gym in the town where I lived, but luckily, I had an old clothesline in the backyard, and the clothesline post worked for me to practice pull-ups on.
What I did was grab the bar and jump up to get my chin above the bar, then lower myself down as slowly as I could. In the beginning, I just did this to the point of fatigue. Pretty soon, I could do one pull-up, then two. I would just do as many pull-ups as I was able to...then, switch back to jumping up above the bar and slowly lowering until the point where I couldn't control lowering myself. When I reported, I was able to do 10+ (I wanted to make sure I could still do 7, even on a bad day.) I did the second highest number of pull-ups of the crew that showed up. The person who did the most was also a girl. Many who showed up, both men and women, had not taken the preparation packet very seriously and thought they could just do everything without much preparation. They didn't realize that what you could do when you were fresh wasn't similar to what you could do when you were already tired. Some failed. Determine that you will not be one who fails. Don't use the excuse "women don't have much upper body strength" and not try to do the best you can. I am a small-frame woman in her mid-40s who doesn't have a gym membership, and I can still crank out at least 5. Since I started doing them, I have never allowed myself to reach the point where I couldn't do any. I don't want to feel weak again. Realizing I couldn't do any made me feel weak.
You probably don't have a handy clothesline like I did, but they sell a bar that you can put in the doorway. That's what I use now. I think it's called an Iron Gym or something. You can find them at sporting goods stores or on Amazon. You just put it up in the doorway when you want to use it, then remove it when you're done.
You have plenty of time to ace the pull-ups. Just determine that you will. You got this.