Font scales problem on 7.1 looks not the same in different devices

My font scales down in size when I reach a certain browser pixel size. You can see in the screenshot how it shrinks and moves to the next line if I drag the browser window in. Also, it looks much better on my computer than on my client. computer she is always fixing the gab between the texts. Is there any CSS code that can fix this problem? I have tried everything else.