Swimming newbie training regimen

Does she know how to swim in the sense of knowing how not to drown, or having a decent freestyle (front crawl)?

(Either way, getting somebody knowledgeable -- a swim coach -- to look at her swim stroke would be a good idea.)

If the former, then learning a good freestyle stroke is the first order of business; then worry about swimming the distance of the sprint tri (which will come easily at that point).

If the latter, then, really, anything that gets her swimming regularly is going to be a massive help.  Probably any beginner swim workout program or the swim part of any beginner triathlon program (and there a zillion of each on the web) is fine.  Just swimming regularly is going to produce massive gains early on.

In any case, focus on doing sets of shorter distances, such as 50s (yards or meters) or 100s.  For example, 5x50 with just enough rest between to recover, or if that's too easy, 10x100, or 10x50, or whatever.  It is tempting to think that you have to focus on 'swimming the distance' a lot in practice.  That's wrong.  So if the target tri is a 600 yard swim, you will possibly be tempted to swim that distance a lot, 'for practice'.  Don't do that.  Maybe you swim it once or twice, as a confidence-booster, but you will make better gains by swimming sets of shorter distances.

And if you can find a good swim coach, even if it is just for a few sessions, do it.

Swimming is like a lot of other things where repetition reinforces the action.  

If you're starting with bad form, repetition of bad form leads to stronger bad form.  (yea, you might get through a swim of any distance)

If you can learn good form, i.e. have someone watch you and coach you, you'll reinforce good form.  

Focus on short efforts where you can maintain form.  25 yards and rest, 50 yards and rest rather than 50 yards with good form and another 200 of thrashing.  

Look for adult group lessons, a Master's swimming group (some do more instruction, others expect you to already swim well), or even ask someone who you see swimming well.  You might ask the lifeguard WHEN OFF DUTY but don't ask him/her while on duty as they've got a responsibility to watch the entire pool.