One other thing worth mentioning -- at schools where recs are necessary (I know nothing of the OP's campus, but also thinking of another recent thread on this topic):
An alum will often offer to a write recs for PNMs she knows, and in these cases, the alum probably has a good idea about the PNMs' scholarship (and other qualities) before she offers.
But in the course of gathering recs (especially multiple recs in large Greek systems), PNMs may ask alums they don't know as well for recommendations. When the alum agrees, the PNM assumes a positive rec will be written, and rightfully so.
When the PNM (with a low GPA) then passes along her recruitment resume, this is what jumps off the page to the alum:
2
Which can be awkward for the alum if she knows that her group cannot or will not (perhaps sans some special circumstances) extend a bid to the PNM with a GPA anywhere in that "2" zone, because that rec form also has an area where the alum must endorse/recommend (or not) a PNM for membership.
If an alum does not know the PNM well, she will not be aware of any mitigating circumstances surrounding a low GPA (if any), or of any special connections (if any) a PNM has in a chapter. She may not even make the PNM aware that her GPA is an obstacle in recruitment in general, and just complete the form as an info only/courtesy rec but without an endorsement for membership.
So potentially while the PNM may believe that she has a positive rec to this alum's chapter, she actually didn't receive a recommendation for membership. An alum can also send a "no" rec (not recommending a PNM for membership) based on a low high school GPA - she may not feel a PNM is quite ready for college-level coursework AND chapter obligations.
Most alums will do what they can to help a PNM, including passing along special circumstances if these exist, but there isn't much most alums can do to overcome a low GPA when their chapter has higher selection criteria.