During my first year here, one of my former co-teacher's grandmother had also passed away. I wasn't close to this co-teacher, though, so I didn't give any money or anything. Also, around the same time, the mother of another English teacher at my old school had passed away as well. She wasn't my co-teacher yet at the time, though, so since I didn't know her very well yet, I didn't give any money, either. In both cases, I don't think anyone expected me to do anything (e.g. give money), since no one (my other co-teachers at the time) told me to do anything. However, in your case, I don't know if you are close to your co-teacher or not. If you are, then it might not be a bad idea to give her something -- if not money, then at least a sympathy letter would be nice and I'm sure your co-teacher would appreciate that.