You have got to keep your own strength up. I have suffered from depression and I have several friends who dealt with depression and panic/anxiety. There is help and you may need a number of different approaches to deal with it.
One of the very hard things about getting to "a certain age" is that you start to deal with mortality. In some ways we don't feel that we are getting older, yet those around us are. A lot of us go through phases of losing a lot of people - that happened to me as a teenager. I would get up, see a suitcase opened up on my mother's bed, half-packed, and I would go downstairs and ask, "Who died this time?" And off we went to another round of funeral activities.
Your feelings are made worse by a sense of being out of control. If you have OCD, that's an attempt to exert greater control over things - many of which are beyond your control anyway.
You need to be careful about google - you get all kinds of information that may or may not be helpful. It may make more sense for your to go to one of your mother's appointments, if you think you can handle it and not be one more person for her to take care of.
Your mother smokes. She has taken on a whole set of risk factors that are beyond your control. If she is addicted, she may feel it's beyond her control as well.
Your daughter is seeing you in ways you don't even comprehend. Do not think you are shielding her from this. Your anxiety is going to be palpable even to a young child. You need to get help.
I have a a few friends in your neighborhood who has done very well with nutrition to help her health issues. You can also benefit from counseling to help you cope. Do this for yourself and for your daughter.