What is the ruling on a girl's refusal to marry due to her promise to the suitor, knowing his current inability to marry her, yet insisting on waiting and contenting herself with infrequent text messages exchanged between them?

There is no blame upon the girl for rejecting suitors while awaiting your proposal, if you intend to marry her once you meet the requirements. However, a relationship between you two is not permissible before the marriage contract, even if it is merely exchanging messages, due to what it might lead to in terms of Allah's wrath. Furthermore, a girl repeatedly rejecting suitors and a prolonged waiting period are not without potential negative consequences.