Etiquette regarding multiple letters of recommendation Several months ago, I was undergoing the process of transferring to another university overseas, and I asked my undergraduate adviser if she could write me a letter of recommendation. However, since she gave the letter of recommendation to me (I was supposed to include it in the mailed transfer application), I've had some money issues, and now I'm not entirely sure that I'll be able to transfer after all. If I don't transfer, I will be applying for various scholarships/internships at my current university, most of which will require letters of recommendation. 

I'm pretty close with my adviser and I think that, out of all of my professors, her letters of recommendation would be the most genuine/positive; however, I feel like asking for two/ letters of recommendation over the course of several months gives off a negative impression, especially since I didn't even end up using one. I don't want her to think that I'm unreliable or that I don't appreciate the time/effort that went into the first letter. Taking all of this into consideration, should I ask her for another letter of recommendation? And, if so, would it be possible for her to just modify the first letter she wrote me so I don't waste too much of her time?
Yes, ask her.  Advisors know that they will be asked multiple times.

Yes, she can modify her previous letter.  That's the beauty of word processors and a hierarchical file system!