This kind of behaviour can be symptomatic of someone wth ADHD. I write this as someone who has ADHD and does have a tendency to do what I call 'yammer'. Thankfully, I do realise that I do have a habit of doing this, and, I hope, I am quite good at shutting myself dowwn.
If it helps, I find I have the biggest problem if I am upset or stressed about something, I would think that if I hadn't seen or spoken to someone for a couple of days, I might well ring someone up - and then talk non-stop.
On Monday I had a hospital appointment I was very nervous about, and I was conscious of talking too much when I was witht he doctor, so I did my best to shut myself down.
However there are ways of dealing with itMy DD, who is also neurally diverse, although I am not sure what 'umbrella' she comes under, lives alone(by choice), but tends to ring me when she is upset and talk for hours. Over the years I have developed a technique, which helps to slow her ddown and end the rant.
The first thing to do is let the raanter rant for 10-15 minutes, then ask her something about another aspect of her life, so she has to pause, and reset her mind. perhaps ask, about children (if they are not the subject of her rant) or her garden of shopping. You know the person, so know what their intersts are, then slowly widen the topic of conversation to make it more general and two way. I find this method works very well with DD, so it might work with others with this tendency.
By the way, I have a very good friend, who if I start yammering just turns to me and says 'M0nica' you are yammering, shut up.' It works very well, but then you need to know someone well, to know that a response like that is acceptable and will be laughed at.