How old is she, what breed and what is her body conditioning and did you buy her as a red heifer or raised her yourself and had you supplied her with mineral?
I'm inclined to forgive a heifer and while I am not there to assess the situation or see the calf, I would consider supplemental feeding before I would totally pull a calf but that is a decision I would base on circumstances and that doesn't ensure that all will be well. Did consult with a vet or consider a shot of oxytocin.
If you purchased her as a bred heifer, I would base my decision on the care and condition she received prior to your ownership, if the calf was premature and also if she showed any maternal instincts at all. If it is a heifer, I raised, I base my decisions on lineage, maternal skills of her mother and if she showed any maternal instinct at all.