The div is a block-type element, and by default occupies 100% of the width of the screen, or the element it is in.
See in the example below that I put it with 15% of the width of the parent, which in the case is the body, which by default is 100% of the screen width ...
EDIT: In the example I made, leave the div, with a minimum width of 15% and a maximum width of 25%, so if the content is small it occupies at least 15%, and form greater than 25% the line will break.
NOTE: I used position:absolut
to place the chat in the lower right corner
.div-chat-i {
color:#000000;
background-color:#C6E2FF;
padding:5px 12px;
border-radius:10px;
border:1px solid #ddd;
/* estilo de posicionamento e largura*/
min-width: 15%;
max-width: 25%;
position: absolute;
bottom: 10px;
right: 10px;
left: auto;
}
<div class="div-chat-i">
<p>Lorem, ipsum dolor.</p>
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Numquam asperiores ratione adipisci dolorem animi ut.</p>
</div>