It makes perfect sense that you wouldn't want to tell people what's going on. It makes things a lot easier in the moment when you lie. You don't have to explain yourself and stick your neck out to see if they'll listen or laugh, you don't have to risk possibly crying in public, and you don't have to feel guilty for "making someone else carry your burden". These are the beliefs i struggle with whenever i find myself lying to people saying "I'm fine".
BUT it does not do any good because in the long run you do in fact need to tell someone. I used to be fearful of how people would choose to respond because my peers used to make me out as a joke most of the time. I could never feel comfortable crying in front of anyone except my dog, Max because i felt inferior and whiny because that's what my dad taught me to believe about tears but he was wrong. I also used to struggle with letting other people know because I didn't want to be viewed as the attention seeker or make other people feel bad for me, but it doesn't affect others THAT much, they'll just be kind of sad with you for a bit because they care and then walk away, letting it roll off their back, and maybe even feel better because they helped someone other than themselves, even if its only a small sacrifice for them.
Then I also realized, you don't have to tell everyone, just one person you trust is enough if you choose the right one, and my mom was the best choice for me because I will always be her beloved child, whether my heart really believes it or not and I'm making a very very gradual recovery.
Some moms can be really awesome sometimes and yours seems like a great one.
Sometimes its better to go up to her and bring up the subject yourself, that way you just have to say "Mom, I really need to talk to you about something very important... " instead of being put on the spot and having that reflex to lie.