AIO my 1 year old found drugs at my mom's house

Am I overreacting or even under reacting?

I've been visiting my family I stayed 1 week at my sister's and 1 at my mom's, my mom's drug use has been a big elephant in the room for years I confronted her about it when I got pregnant with my first child who is now a year old. We didn't talk until a month or two after I had the baby because she blew up and accused me of lying and making up stories. We ended up talking and I told her she needs to do better so we've been okay the past year and she seemed to be doing a little bit better but not 100% but still never acknowledged that she has a problem. Well the 5th day of staying at my mom's my little one picked up a container that was red and rubber and was about to put it in her mouth when I noticed and said bring it here as soon as she brought it my heart sank and I opened it and there was meth and pills. Thank God she brought it to me, thank God it was a closed container. I was furious and also shocked and in disbelief I called my sister and she said she would come get me she was also in shock and my husband was furious. My mom was at work when this happened so I just started packing things up and waiting for my sister and my mom to get there. my mom gets there I confronted her and she acted like she didn't know what that was and was blaming it on her mechanic who was there the day before and had literally sat where the baby found it so I'm sure it was his but the fact it was even in her house and the fact she had someone like that in her house which is a normal for her since she's using herself. I only got one I'm sorry followed with a lack of accountability and then tried to gaslight me that I was being dramatic because I had called my sister to pick me up and was leaving. That same day she texts my sister for help with figuring out her insurance like what happened that day didn't happen. She has not texted me anything.

I agreed to sit down and talk to her with my sister and basically this is the final straw she needs to stop lying to us about her drug use and get help but I doubt it is going to do anything.

I feel like I'm still in shock and it hasn't even fully sunk in that this happened. I'm hurt and upset but I'm aware this is absolutely not okay and my daughter will never be in her care or go to her home ever again. I just don't know if I can completely cut her off. She's my only parent and my mom is not a bad mom but she's by no means perfect. Im now at my sister's and will be flying home in another day. I cut my trip short and will probably not be coming back to visit in February like me and my husband were planning. This just sucks so bad and all these feelings are battling in my head and I don't even know whats the right way to handle this. I know my daughter comes first and I have to focus on my family but like damn that's my mom? She's all I ever had. And she is a ride or die type of mom but the drugs have just really messed her up.

Am I overreacting? Under reacting? Any advice from someone who's gone through something similar? Please help.