Whether or not gender is a social construct, society as a whole buys into it. The fact that society attaches certain (wildly incorrect) assumptions to me because of my body causes me discomfort and dysphoria, and that suffering is real regardless. It doesn't matter if gender identities are social constructs - as long as society relies on those constructs and believes in them, people who identify as trans are going to have problems. So whatever your friend believes, she needs to acknowledge that your suffering is real, no matter where it comes from.
Also, as everyone else has said, if she won't respect your feelings there's not a lot you can do but cut her off.