Front or Rear Drysuit ??

Rear zip - without question. Less bulky and she'll have her helm to help zip up when a changing room peg is inconveniently positioned. the trident link above looks good to me.

whilst I personally find a wetsuit best nowadays, there have been times when crewing a trap boat when frankly i've been spending far too long in the water in winter- that is when a dry suit is a good idea. plenty of MPS national champions have worn them and despite what iGRF may say, they're not a bunch of nancy boys. Besides there's no point scaring off a teenage girl and telling her to 'man up' is there? & £300 sounds like a cheap way to numb the moaning & whinging from the back of the car on the way home every Sunday.

I seem to be out on a limb here, but I am very happy with my front zip Gul Shadow. I find it no more restrictive than a wetsuit on a Contender,  perhaps less so than a wetsuit and several layers underneath. And it is warmer. The time that really shows is coming ashore and sitting around for lunch when it's cold. You always get at least the legs of a wetsuit wet and sitting around leads to chill. That doesn't happen with a drysuit.

If she's getting cold, then either more layers, a better wetsuit, or a drysuit are called for.
I prefer a drysuit for sea sailing from about now to March or April.
Particularly when sailing trapeze boats, as the spray and windchill really affect you.
As does waiting around between races.
Front entry suits tend to be more convenient, but most 'Ladies' suits have a back zip to avoid a zip across the chest. with a trapeze harness, that may mean the zip is pressed into the back by the harness.
A friend of mine has a drysuit with the zip across the front of the shoulders, I think it's a magic marine but I'm not sure.

You will always find people who don't need drysuits, but if you are the sort of person who gets cold and doesn't like it, they are a reliable solution.

Personally, I'm on my second Typhoon front entry and would buy the same tomorrow if needed.
Cost per outing is probably not much worse than wetsuits.
I would suggest finding the make that fits best, as some seem to have weird leg:body ratios IMHO!

yes.  I have a front entry dry suit for coaching, safety boating, instructing or sailing the grumpy old kestrel, but for anything more sporty it's back into a decent wetsuit with the right layers underneath, with hot socks, hat and good gloves.  

Really is no right or wrong to this one.