I don't know if I can help much but I think she should take her time with it and do what she can in her ability at the moment. You don't gain a lot of customers overnight, I'm sure that takes time. But then again I don't really have a business standpoint over this because I do commissions and post my art online just for fun right now.

But as an artist who can be very anxious even as simple as posting my art online, in my experience that takes awhile to be comfortable with. Eventually I believe your friend will get there, maybe right now she needs to find out what works for her.

Honestly getting commissions is the hardest thing for an artist...the best thing I can think of is for her to (1) keep drawing on her own to improve skills and (2) to advertise/post said art on as many platforms as possible ie: instagram, twitter, tumblr, da, forums, etc. Having friends spread word can help too but even I struggle with getting commissions...

Don't push for 'em.
Literally art. Post somewhere. Have a mention like 'I'm available for commissions', but don't push it.
If no bites come, continue arting, continue improving your work, and keep posting. Keep posting. Etc.
Eventually clients will come.

Or step into the NSFW market as there seems to be more work to be paid for in that area

Edit to add:
If she comes off as pushy with it, it will eventually drive people away. Not that I think she will, intentionally, but I deal with social anxiety myself and sometimes my offhand mentions when I submit somewhere, it can come off as being so awkward it's begging.