What she said is incorrect. I'm about as strong as most guys in my gym. I can bench the same amount that you can, but know that's because that's a realistic amount for someone who is starting out bodybuilding and isn't blessed with extremely lucky genetics. I've also been on HRT for much longer than you have. My problem is more of that I avoided the bench for a long time, because I've always had no one to spot me and that scared me for a while because I'm a tiny guy. I've just recently gotten over it though.
You have testosterone pumping through you and yes, that will help you with bodybuilding, but being born with a body that naturally produces estrogen won't make you necessarily weaker than biomales. What you really should be considering is your genetics, your diet, and the type of workout you currently have when considering matters of strength.
Other than all of this, you should probably look into seeing a family therapist to get those issues with your mom sorted out though. She seems to have some issues with you transitioning, whether she openly admits to it or not.