Are local transactions taxable?

My sister and I usually borrow money from each other so basically I send her money and she pays it back after a few weeks and vice versa. It's not much but eventually adds up in a year.

I'm not sure if this falls under the gift tax, and should I just make sure to not go over the 1.1mil threshold annually or I don't need to worry about anything?

I really have no idea so if anybody can explain it would be very much helpful.

Edit: We also send money back to our parents and we kind of take turns so sometimes, so we usually send the money to whose turn it is and just send the money abroad.