Hi everyone, just a general question here about 2 little dogs

My yorkie, Cookie (he), will be 3 months on the 10th and the maltese (she), Luna, will be 3 months on the 21st. I was reading other posts and it seems to be that their "fighting" is really playing. I was just concerned because she seems to be really aggressive but he doesn't cry out so I guess they are playing.
I just have one question though. She is really aggressive with us as well. I thought it was because she was teething possibly but she snips a lot and when you yell at her or try to get her to stop something, she becomes angrier. Any advice?