To add, just saying, "I'm a female" may cause the trans listener to infer that you believe that, unlike you, she is not female - depending on how defensive the person is, of course. Some may appreciate a "too" following a statement of your femaleness, while others might find it patronizing. However, I'm sure most mature people would recognize that you're just trying to make them feel better with that word; if not, then it's a shame that they are the way they are.
It's an important note that the trans community, because of how it is often mistreated, finds ways for various addresses to be seen as hostile simply out of a desire to protect one's own emotions, and/or in the extreme, one's physical self. The experiences we have, ourselves, aren't even all that important in the age of the Internet - even a person belonging to the trans community with a very normal life can feel mistreated or victimized simply through the experiences of other trans individuals.
In any case, on the subject of your 'HRT', it's not likely that your body will feminize all that much with the aid of more or different hormones. Since you are a cis female, you probably still produce enough estrogen to keep feminine attributes, and you probably don't produce enough testosterone to offset that much. PCOS certainly does cause unwanted hair, but aside from that... there likely isn't any other noticeable effect that can be seen from a reduced amount of estrogen to reverse by your HRT. It depends on the individual, of course, but unwanted hair is usually one of only a few (or couple) masculine-appearing symptoms.
To note, the shoulders themselves don't shrink in MtF trans people, but rather the muscles in that area - it's still a loss of shoulder broadness, but the bones are set in stone unless you're very young.
If you still want to bring up the HRT that trans people utilize with your doctor, then often it's spironolactone and estradiol-17B (Estrace being the most common brand). Cyproterone acetate is another androgen-antagonist that's used, but not within the US, and usually as a "plan B".