3 1/2 months isn't exactly a long time to be an assistant.

I would stay if these things were made clear:

The owner/stylist can give you an approximate time you will be an assistant ( 1 year, 2 years or what have you)

Then I would insist on training- color, haircutting etc- not just nails.  This is what you have to think about- if your practice makes perfect with the clients you are working on now, they will be your regulars when you are bumped up from being an assistant.

However, if she is treating you like a manicurist and not giving you any training- only services she doesn't want to do, I would insist on commission- or work elsewhere.

It is crappy.  There is another person making commission on your work!  But besides that point, Those tips are yours!!!  If a waitress in training takes a table by herself would she give the tip to someone else?  I don't think so.  Tip money is from the client to you for doing a good job.  If a client tips you for a shampoo do you have to give that up too?  If you are not aloud to except tips you should be telling the client just that.  I don't think they would be happy to know the money they are dishing out for you is going somewhere else. 

Don't get me wrong I think its great that your salon has this training program and not sending new stylist out to the sharks.  But many salons offer training and assistant positions to new stylist.  If you are thinking about switching salons do it soon!  Before you start to build decent clientele. 

P.S. Keep in mind most people hate doing pedicures!  I'd have to say if I could pass them on to another person in our shop I would!