Well, are you considering NOT doing this then to avoid coming out?
If not, then... it's inevitable at some point. BUT, it's not like you have to tell everyone right away. You can get into therapy first and sort everything out, make sure this IS what you want, THEN start planning coming out strategies. You can be months into HRT, have strangers occasionally read you as a female, and STILL those close to you (who see you often) might not notice. It took me a year+ from starting therapy to get to the point where I pretty much have to be coming out now. Everyone has a different experience of course though.
BUT, are you married? If so, and IMHO, she deserves to know (if she doesn't already) - and sooner rather than later.
Kate