I'm so sorry to hear of the death of your grandmother, but your family is right. Now is not the time to worry about losing weight. You're in a very fragile state and still mourning.
Gaining some weight does NOT make you a bad person. Here's the thing, good health isn't just about losing weight. If your head is not in a good place, you won't lose. If you're experiencing a lot of stress, you won't lose. This isn't a diet. In order to take the weight off and keep it off, you must be ready to make this a life style change.
Instead of worrying about trying to lose weight, start with some simple changes for the time being. Don't try to do everything at once or you will end up frustrated. And definitely don't look at good health or weight loss with an all or nothing mentality. If the only healthy thing you did for yourself today was drink 8 glasses of water, that's still a step in the right direction.
Just start with a couple of simple changes. Don't beat yourself up if you want pizza. Do this. Have a slice of pizza, but pair it with a BIG leafy green salad. Sit and savor that piece of pizza. Don't inhale it like a Hoover. Take your time to enjoy it. The faster you eat, the less likely you are to taste your food. And when you can't taste something, you'll keep eating until you do. Try to slow down.
Because you're under stress, this is when you really need to take care of your body. stress can break down a person's immune system and make them sick. Don't let that happen. Take baby steps literally and figuratively. Just a few simple changes. Try to drink more water. Try to take a walk each day. Try to eat more veggies. that's all. Every little bit really does make a difference. You have to believe that.