I don't think that at that time she had a difficult material situation, as it seems she still has her small properties around Birmingham. She confessed in the letter she felt "on the shelf" and knew no other young man than George. However, the "timing" of her engagement shows complete lack of care for her previous declarations and promises from the days of Duchess Road. If her engagement would have been already consummated by marriage before Tolkien's 21st birthday (or if she postponed any engagement or involvement at all until that date), she would have had a higher standing in this matter
. As such, her lukewarmness shows she is simply ... drifting. Compare this to Tolkien's torment, as it appears in the letters. Of course, it all worked out for the best in the end, and that is all that matters.