My best guess is the cat is getting hyper, then because it's hyper, it's trying to get attention by biting. If this is the explanation, then your mother might be a particular target due to her habits being coincidentally and unfortunately conducive to the behavior. By that I mean, maybe her usual spot is a convenient location for her to be a target, or perhaps while you quickly notice the cat and play with it, she is failing to notice quickly enough to satisfy it, which makes it want to use the bad habit of biting to get her attention, or something like that. At any rate, cats definitely are smart enough to learn different people's habits, and interact differently based on what they know of the person they're attempting to interact with. As for how to deal with this problem:
Play with the cat more.
The more you tire your cat out, the less it'll randomly become hyper. Cats often run on a predictable schedule, wanting food, sleep, and play at certain times, which is probably why you've noticed these incidents usually happening at a certain time of day. Use that to your advantage and play with the cat starting at or a little bit before that time of day your cat tends to start its routine of running into the bedroom and biting.
Keep your reactions to a minimum.
If it is an attention-seeking thing, then any reaction might be encouraging it. I realize that it's not possible to completely not react to getting bitten, but try the best you can manage.
Learn your cat's tells so you can be more proactive with play.
Closely observe your cat for a while to see if you can observe any signs or patterns that you can look for that means it's getting hyper. Cats often get the most hyper around mealtime, for example. Or you might observe some particular body language that indicates it's getting hyper. For example, you might notice the cat is stalking you or tracking you with its eyes. You might even try experimenting by playing with it at various times, and with the cat in different moods, and taking mental notes on when it reacts the most to your attempts to play. All this is so you will know your cat's signs better, and then later when you notice those signs, you'll know to get the toys out.