I'm kinda in a tough spot... I don't like it when people are dishonest with me and I always try to…

I'm kinda in a tough spot... I don't like it when people are dishonest with me and I always try to my hardest to be honest about everything. But my would be mil is a compulsive liar and I don't know what to do about it. We had been trying to get ahold of her for 4 days and she didn't text back or call back, and then she randomly shows up last night and says "oh my phone isn't working for the past two days" and then all of sudden today the day she needs help babysitting my bfs 4 year old little brother at a parade her phone suddenly works!! I know she's been meeting up with these big time drug dealers too and I'm sure she's back to taking t3s again. I don't like spending time with her because I'm so pissed off at her dishonesty. She was supposed to be here at 10:30am and didn't get where until almost 11:30 making my bf late to do his job. Should I keep my mouth shut and allow her to keep lying to mine and my boyfriends face or should I confront her and figure why she feels the need to lie to us all the time??