They won't stand for being mistreated and will either confront you or cut all ties if necessary.
They are helping you out a lot, therefore it's only fair that you help them out in return. They believe it is only fair that you provide the same amount.
They will become rude to you because they resent the way you are treating them.
They will worry that they are failing in some way. They'll start to take the blame for what's really your fault.
If you can't meet their expectations and provide them what they need, they'll lose interest in you. After all, nobody likes wasting time.
They refuse to believe that this person isn't right for them and instead insist on doing all in their power to win that person over.
It's a huge drain on their energy. They will be completely spent and unable to continue fighting.
Until you take the initiative in talking to them and asking them out, they will cease doing so.
They won't say why they're angry with you specifically, but their silence will be a dead giveaway.
If you flirt with and/or date someone but don't make time for them and treat them well, they may see this as a lack of commitment on your part.
They will need explanations. Even if they decide to leave because of this issue, they will still want resolution.
It's possible they'll cling to you for a little while longer, but they won't be in this state for good.