Emailing a potential Ph.D. advisor before the start of an M.S. program?

[Cass]

Ok, so the situation is that I emailed a few different professors that I thought I'd be interested in working with when I was applying to Master's programs. One of my top choices answered pretty quickly and was very nice and encouraging, but said she wouldn't be able to take any more students for a while. I thanked her and moved on. 

Flash forward to being offered an internship in a University medical and veterinary entomology lab (this is the field I'm hoping to get into) through the state's Department of Health and then being offered a graduate research position at that school. So far, so good. 

While the department is pretty good and my current advisor is fantastic, I have no plans to continue on to do a Ph.D. at this school. This is partly because my degree would say "entomology and plant pathology" and that feels deceptive since I have no intention of actually working with plants and partly because I think it would be good for me to gain experience in different labs working with different people. 
 

So, back to the professor I emailed a while back who said she didn't have space. That school, and her program specifically, is still at the top of my list. It's a very good school and would, at this point, be a serious reach for me. However, I have more research under my belt than I did when I first contacted them and I have the entire 2+ years of my Master's program to improve my standing. I've been told that, since I've already spoken to her and I'm pretty certain this is what I want, I should contact her as soon as possible- maybe even before I start the Master's program- to let her know what I've been doing and tell her I'm still interested in working with her in the future if she has the space. 

My questions are: 1) is it a good idea to contact her again this early?  2) What should an email like that say? 

Any and all advice is appreciated. Thank you. 

[sarab]

If you are planning on working with her in the fall, I don't see why you shouldn't email her. Go for it!

[Cass]

I'm not working with her in the Fall. I'm working with the professor I did the internship with in the fall for my MS. For my Ph.D. I want to go to another school with the professor I'm thinking of emailing. If I work with her, which is definitely not a sure thing at this stage, it won't be for at least two years. 

[geographyrocks]

You could send her an email now, but what if you change your mind?  Even if you don't change your mind and know you won't, she might have the same thought that I did.  I doubt that you will continually email back and forth for two years meaning she might even forget about you during that period.  To preface my advise, I want to note that I do not have experience with this. 

 

You could email her now thanking her for her time and advising her of what you're currently doing.  In a year or so, you could email her again advising her of the research you have performed and how you are doing in your program.  That will be about the time that you would start applying for graduate schools anyway, so it would make sense.  You could also her ask her at that time if she thinks she'll be able to take on more students.