Like the others said, this is a very stressful time for a student, including your friends. I'm sure your friends do not understand depression, which doesn't help you at all. I really can't believe your mother said that to you. So, like Darren said, use that as motivation to prove her wrong. You've made it to grad school, so you are certainly not a quitter.
A lot of us suffering from depression have a hard time during the holidays and I think students dealing with depression have a tough time during first semester finals more so than spring ones because of the holidays.
Please know we are here for you and consider us your HealingWell family.