My observation on this is that even if the facts were presented to you, including the OP, that you would be so stubborn on your position that you wouldn't take those facts into account and would firmly stand by your current viewpoint not open to that being challenged or altered.
If then daughters are unable or don't want to engage in proving you wrong, why not do your own research into views that challenge you or you don't agree with? There's plenty of reliable information out there.
There was an interesting study published in 2018 by Stonewall about Trans in Britain which is full of statistics and answers a lot of questions.
stonewall.org.uk/system/files/lgbt_in_britain_-_trans_report_final.pdf
What I find frankly frightening in this thread is high levels of misunderstanding, misinformation and perpetuated viewpoints and language which as a result contribute to the discrimination that trans people face. Indeed, their rights are no more important than anyone else's but neither are they less than. In a country where we all have the right to safety, housing, education, access to healthcare, right to work, right to being treated with dignity and respect and to not be discriminated against including being harrassed, bullied, attacked verbally and physically, sexually assaulted and murdered trans people are attacked on all fronts. This DOES NOT take away from the struggles that any other protected group faces.
The instances of violence towards women by trans women are such a minority of trans women and do not fairly represent the trans community. Trans women are more likely to be on the receiving end of misogynistic violence than to be perpetrating it. Most of them just want to live their lives and be safe like anyone does, it is not asking for more rights than anyone else has. Patriarchal violence damages us all and so we should stand together.
Sex, gender and sexuality are entirely unrelated factors and multiple genders are recognised in many cultures around the world and have always existed. Just as trans people have always existed.
If you are looking at sex as purely down to genitals and chromosomes, then you will find that there are many variations on xx and xy. Almost 2% of the human population are also intersex, which is the same amount of people with red hair or green eyes, so this is not rare.
Gender dysphoria is something many trans people experience especially when growing up and can have a profound impact on someone's mental wellbeing. Puberty blockers have helped many people experiencing this and reduced the rate of suicide by giving people gender affirming treatment or by buying them time. Puberty blockers are not a permanent treatment, once you stop taking them either puberty kicks in or a person may go on to hormone treatment when they become an adult. Trans people also have to go through years of counselling before treatment is agreed. Access to medical treatment is literally saving people's lives so access to healthcare for trans people is essential and time critical, just as for any other critical lifesaving healthcare and mental health support. This is NOT saying their healthcare is more important than it is other people.
In terms of language and names, I have a couple of points. Using people's deadnames cannot be compared to changing a name when you get married, as someone here tried to do. The reason it is traumatising for people is that it doesn't acknowledge the gender dysphoria and experiences related to that name. This, along with using the incorrect pronouns, adds to the experience that they are not accepted or safe. It is not difficult to expand our language and be inclusive, it does not erase female identities such as mother or breastfeeder, simply gives us additional language so people of all genders are considered, included and recognised as is their right. By refusing to acknowledge someone's name, gender, or pronouns this is a form of discrimination.
Why should we, as cis-gender women, not want the same rights for others that we have so hard fought for ourselves? We only add to supporting patriarchal ideals by refusing to acknowledge the fluidity in gender and how trans issues are feminist issues. By saying you are "gender critical" you are refusing to acknowledge your viewpoint is discriminatory and therefore severely damaging to the group you are discriminating against. Many people here saying they have a right to an opinion and a right to challenge and disregard the gender of people who are openly trans and in "women's" spaces fail to see that they are re-enacting the same violence and discrimination that cis-women have experienced and feminists have fought to change. To be a feminist is to challenge the patriarchy and fight for equality for all. Trans people suffer at the hands of patriarchal ideals and violence daily just as we do. It is unfair and uninformed to claim that trans women are just men demoting themselves and then trying to claim the struggles and rights of cis-women and that they have the same rights as men, this is narrow thinking and untrue.
Having a viewpoint is one thing. Having a viewpoint that constitutes discrimination is unacceptable from both a legal and moral standpoint and we all have a responsibility to not discriminate others.
I would really urge anyone here who is opposing trans people, particularly trans women, and their rights to spend some time researching and reading opposing views and considering actually how patriarchy and misogyny damages us all, and critiquing how we may be unconsciously contributing to what we say we stand against as feminists.
Now, I imagine I'll be in the firing line for this but why ask the question if that's the case? You want to know why your daughters call you a terf and can't explain things to you. If you're actually interested in a discourse and not just participating in wedge politics, and understanding your children's viewpoints, then I ask you to consider what I have said and think it through, do some more reading of your own to try and underatand them. I hope it will help your relationship with them, even if you can't ultimately change your views.