B1- application time and chances of approval

[richmond]

My mom's I-94 expires on 28th Dec. I want her to stay for 1 more month (basically spend the holidays with me). She has a 10 year multiple entry visa and this is her second visit to US. I have 2 doubts about applying for an extension for her B1. I would really appreciate if you can provide any insight:

1. How long the application takes? Will it is okay to apply now or is it too late? (I read some accounts that it takes up to 3-4 months).

2. What are the chances of extension request being denied. She is not planning to stay permanently, but I was very sceptical about applying when I read that it will cancel her multiple entry visa and she will have to apply afresh.

Thank you very much.

[immihelp]

1. It takes 3-4 months. You can apply any time before the current I-94 expires.
2. There is no way for anyone to tell you the chances accurately. It all depends.