This is typical behavior and yes, covid has a lot to do with it. First you must always exemplify the behavior you wish to see. Second, she is your granddaughter and not your daughter. You can tell your daughter privately that this fighting hurts you in your home. You can, as the owner of the home, hold a household meeting at a designated time. Have an agenda written down to follow, and give them each a copy at the table. Make a list of house rules to follow for all of you. It can be designated chores, or choice of chores. It can be all fights must take place in a bedroom, not in the main part of the house. Consequences are they have the choice to move out. If your daughter lacks parenting skills then ask her if she would like your advice. If she says no, then honor that but rules for the household hold. Covid is not easy. I fight with my husband over the littlest of things and he downright gets nasty. Remember, consequences for the 13 year old should be the mother's decision. Consequences for your daughter are your decision. You have every right, if you are paying the rent, to expect your daughter to have fights in their bedroom.
The King is to resume some duties.
Misaligned holes in flat pack garden furniture