Mobile version for my app

We have developed Web Site. And for mobiles we have developed native apps(Android, iOS, WinPhone). But there are some users which do not want to install app instead of they prefer to open app on Browser. So our web site is not bootstrap. And in mobile browsers it does not works as expected. For example user must zoom it for search something in content. As we know there are a lot of bootstraps. For example i have used Twitter Bootstrap years ago. But not in this project. And there are jQuery mobile like tools for creating mobile version of site. So my question: When and why use jQuery Mobile for example instead of Bootstrap? I need professional advice.

It will be good to ask to my question over Java Spring. Because our project developed in this platform.