werewolves, you have asked a really interesting question. I am new to feminism but I have just started to understand the concept of intersectionality, which is what I think you might find useful to look up. Yes, all women experience discrimination under the patriarchy but a woman who is gay will experience discrimination because they are a woman AND also because they are gay. The two are inextricably linked.
Feminism is a movement that seeks social justice: equality for men and women. However, when we are looking at issues surrounding social justice there is a term that is very useful to learn about that is called privilege. You can enjoy privileges in society if you belong to the norm or the dominant group. White males, for example carry lots of privileges, such as ease of access to opportunities, power and status. However, a white homosexual man might not carry all of the privileges as a white straight, male, as homosexuals are often discriminated against.
What can often be a difficult but useful exercise is to think about what privileges you carry and then listen to your other group members and try to recognise that their concerns are just as valid as yours, except they are different where sexuality is concerned. Instead of switching off and thinking ''This is irrelevant to me as I am straight, when can we get back to talking about stuff that is just about us all being women'' try thinking ''Gosh, I did not know that gay women have to think about this. I never have to worry about out that because I am straight.'' ''Or, why is it that just because a woman is not straight she has to suffer x type of treatment''? Frame it differently.
I think, if your group consisted of straight women all over the age of 65 you might have found that you ended up discussing issues faced by that age group. Ultimately, a group tends to be led by the make up its members.
Again, we come up against the same issue in feminism where if another -ism comes into the equation it is often deemed as ''irrelevant'' or ''splintering'' to the feminist cause.
Their concerns and issues they face are still relevant to you, as you are all women but they just also have additional discrimination to think about.
By the way, I admire you for actually joining a feminist group!