it sounds like youre in a really toxic and intolerant environment, Im sorry :(
I would recommend getting OUT of there as soon as possible, especially if you do plan on eventually coming out to her. Its understandable that it feels *wrong* to be keeping something from your parents, but you do NOT have to come out if you don't want to/aren't ready to, please remember that <33
I would also recommend (if you do want to come out, of course,) not telling her unless you are financially stable and have a good housing alternative. I don't know your situation, but please keep your safety in mind :( I wish you luck my friend!