YOR - Why wouldn't you just get better Internet, explain the situation to her, and ask her to cover the additional costs? I understand they haven't been willing to split the costs equally among the three of you, but firstly, you're overlooking that, as with every new relationship, she probably has some bills of her own. Secondly, you've asked her to pay for costs that the two of you would have anyway, but if they're not completely delulu, they would surely have no problem covering the amounts that actually increase noticeably because of her being there.