The real issue is to find out, why she does not want you to be away from work. It could be that she feels you or your research are not yet ready or that she knows you are on a though schedule with your project anyway. The reasons might be good or not, they might be valid or not. Talk to your supervisor to find out more about her reasons. Maybe you can address them or convince your supervisor, that you should attend at least one conference per year. If money for travel expanses is rare, you can apply for travel grants, apply to conferences nearby, or pay them from your private money. The experience might be worth the money.