I put my voice recorder on so that I'd have a record of what mom was saying. Is that wrong?

My Mom has gotten much worse today. First I'll back up just a bit. We are blessed to have 2 aides come out 5 days a week one is here for 3 hours a day for 3 days and the other is here twice a week for 4 hours each day. They give mom a daily shower, clean her dentures, help her dress if she needs it. They also do light housekeeping, dusting, vacuuming, Doing her laundry, clean and dust her room, change her linens, cleans her bathroom, sweeps, and mops both her bathroom and kitchen, etc... All this is paid via her insurance company praise God! Because it's a blessing. So yesterday she asked if I'd spot her while she took a shower. I told her that her aide just gave her a bath yesterday and that she would get one tomorrow. I explained to her that Mark *my husband* and I wanted to spend Saturday together. Now today Sunday. I slept in pretty late. Mark told me that mom had been ranting quite a bit and using very terrible language towards him. I got up went to Mom's bedroom and knocked on her door. I asked her why she was talking to Mark like this? Mom said she wanted a shower and demanded Mark to wake me up and give her one. Mark told her no as I had gotten to sleep late last night. This made her angrier because Mark would not do what she told him to right then and there. So here I am at her door listening to this. Mom said I have been in this *expletives* wet diaper for 8 hours (this of course was not true). And I need a shower! I said Mom why didn't you change out your diaper? She said because my thumb hurts. I told Mom that she doesn't need her thumb to changer her diaper. This infurated her. She says well I called the police because you let me sit in a wet diaper and wouldn't give me *expletives* a shower! My Mom needs no help in dressing, changing her clothes or her diapers. She is still very independent in this area. When she started threating us I put my voice recorder on so that I'd have a record of what she was saying. Is that wrong? Because I don't know how else to defend her attacking us! This is the third time she has threatened to call the police in just this week alone. The first time was earlier this week. My daughter had just awkened and was getting to her infant daughter when my Mom stopped her. Mom said Brittany do you know where my wedding ring is? Brittany said no Grandma I haven't seen it. Mom started cussing and yelling at Brittany! She told Brittany that someone in this house took her ring and that she was going to call the police and have them search the entire house for her ring. Second time she said that she was calling the police was because we stole her food! She said we were hiding it from her or that we all sat down and ate it before she woke up that morning. I'm sorry that this is long winded but I felt filling in the details would make what Mom is doing more understandable. So today I started voice recording her when she would come into the room and verbally start attacking us as well as threatening us. Am I in the right to do this. As in my thinking that If I don't record it, it will be our word against hers. I truly don't know what to do! Sitting here in tears.