as the others have said i think if you are going to get them... well you are going to get them but here is what i have tried so far and i havent got one yet (though growth is happening pretty swiflty these days ha ha!!)

- try not to put on weight too suddenly - eat well, exercise for tone etc
- keep skin hydrated - i use a clarins body oil (delicious stuff and my DH uses it to massage me as well - hint do that for your partner, she will adore you for it), i also use bio oil which is good and feels nice to rub into belly now that it is larger!!
- lots of water

Tell her not to worry too much about it though, it is one of those things that just may happen... and it is all worth it. I was v worried at the start and I am honest I wouldnt love it to happen now, but at the same time as the preg goes on I am more OK with all these chgs as preg is such a wonderful time and so i want to enjoy it and not worry too much about these things.