There are many times one must accept their lot in life and in particular when there is nothing that can be done to correct or improve the situation, e.g., a terminal incurable illness. In those cases, one has two choices: accept the situation as it is, learn to deal with the "fallout" and try their best to be happy and thrive in spite of it; or don't make peace with it and live with misery, depression and a generally negative outlook. .
Fortunately, that's not the case with transgender issues. While accepting our situation and striving (struggling) to find happiness without addressing the source of the problem (dysphoria) is certainly one option, the question in my mind is WHY? Why would anyone recommend acceptance alone when there are steps that can be taken that will help address the root cause.
Would your sister's advice change if she knew you had an injury that left untreated would cause you constant distress and misery but with positive action could be greatly improved or cured?
Seems to me she needs to be educated ......unless she is so self absorbed she's incapable of trying to understand gender dysphoria and the impact it has on life and well being. Transition is about taking action to improve quality of life.