Grieving Family and Christmas Pregnancy

I’m anticipating my SIL having feelings at Christmas because I’m pregnant. Tragically, she lost her child a few years ago due to genetic condition and is very vocal about parenthood, loss and grieving. She has helped so many people because of her advocacy.

My husband and I have struggled with unexplained infertility for years. We are finally pregnant this Christmas. I want to CELEBRATE, shout it from the rooftops, wear cute shirts with Christmassy pregnancy sayings on it etc. but I feel guilty doing so around my SIL. In fact, I’m scared to even tell her.

I know what it’s like to wish I had a baby at Christmas, but I do not know what it’s like to have lost a child. I can’t even fathom the pain.

Is there a certain way I should tell her separately? Should I try to curb my enthusiasm around her? Wear baggier clothes? Accept I cannot control her feelings and do what I want to? Looking for advice - please be kind.