You aren't just curious though, you said, she wants it out. Well everyone feels like that in the latter stages of pregnancy but nobody does a DIY sweep because it isn't safe to try and bring on labour when the baby isn't ready.
I don't think you will get the answers you are looking for out of "curiosity" here.
A sweep is basically where you seperate the membranes from your cervix, usually only possible if cervix favourable for labour anyway, or in a parous women.
Its probably not something that is easily manageable for someone who isn't familiar with such procedures so probably best to just stick to gentle cervical massage .. if you can reach. This is perfectly safe and like stripping the membranes will only work if the cervix is ripe and ready.
37 - 42 weeks is considered term and for most babies they are perfectly healthy if they come out after 37 weeks.
There is actually some benefit to going into spontaneous labour earlier rather than later - some of these being - less chance of meconium (statistically higher post dates), smaller baby, more squashy head, etc
However, if your friend is not ready to labour, a sweep will not do much to get her into labour - it can be difficult for a midwife to do and even more so to do yourself, safely, hygenically and without rupturing the membranes - imagine how she would explain that to the midwives! What minkersmum has said is correct but if your friend goes into labour at 37 weeks or so anyway, I cant really see any point to doing it.
Its all down to individual freedom of choice and although I dont necessarily agree with it, I do support her choice if thats what she wants to do, and I am a bit surprised at you getting critisised on here for your question. Some could also critisise women for going very overdue - I have seen quite a few stillbirths due to extreme postmaturity at the labour ward where I work, but that was the choice that the women made, to accept that risk and I would also not condemn them for that.
Sorry that this is a bit long, but I couldn't not comment on this. Good luck to your friend.
Some babies definitely need encouragement to arrive but i agree its often done with haste.
I don't think a diy sweep would cause any problems as the chances of doing it at all are slim so probably no worse than a bit of foreplay.
I would be a bit sad if any women felt she had to explain herself to her midwife for doing something to her own body. Its entirely up to the women what she does as she's the one who will live with the consequenses. Its a day at work for a midwife. Who are we to judge?