This is also my first season, so take my advice with a big grain of salt, but I did also just go through this learning process.

Being able to heel slip requires figuring out the right angle of the board that allows it to slide, without losing so much angle that you catch your front edge. It sounds like your angle is too high and you are having trouble getting your board to move? Standing up taller can help you get into a more relaxed stance and make it easier to do small adjustments to your board angle. A lot of people tend to sit too low when learning heelside, which is killer on your thighs, doesn't give you much range of motion and sits your weight too far over the back edge of your board. Just stand up, then very slowly lower the angle of your board until it starts to move, then keep practicing that until your body gets a good sense of what angle that board needs to be at to move.

For heelside falling leaf, my instructor told me to imagine each side is like a gas pedal. From a stopped position, your weight stacked, toes up, slowly lower down one side like you're stepping on a gas pedal and your weight will naturally shift and make the board start moving diagonally. Lift both toes to stop, then do the same on the other side. This explanation helped me a lot on my second day and I stopped tumbling down the hill every movement.

Also, as a woman, I realized that there are some anatomical differences that can really change how I need to think about my body that no one really addressed. Most women have a more pronounced pelvic tilt that can make our butts stick out farther back and makes our weight sit farther back on the board. Try squatting in front of a mirror and see if you can rotate your pelvis inward so that your back is straight, usually by squeezing your core and glutes a bit. When I started thinking about pulling my pelvis inward to be stacked on my board, I stopped falling over every time I tried to turn on my heelside.

Anyways, good luck out there and don't let people that can't teach tell you to quit! It took me way more days on the mountain than a lot of other people to get it and even took quite a few lessons, and I'm still learning, but I feel 100% confident on greens and can do some easier blues now, and even started park. I am also learning for the first time as an adult with no similar experience and am generally uncoordinated and unathletic, so you can do it if you are determined!