No , you should not trust it. Please see my post 2 above. It explains what this is about and how "she" found you. The reason you share a mutual friend is because the account in question used your friend's friend list to find you. This grants "her" seeming legitimacy as someone you might know.
F.Y.I.: when someone says they are "...out of minutes...almost out of minutes..can't send pics, etc." that means they are using a pre-paid; my guess they are actually a step ahead of that and they are using one of the 3 current "ObamaPhones" Here is where it gets interesting: the "ObamaPhone" they reached me at was never posted on FB or any other on-line site I use. I did know right away it was San Francisco because I have lived in Silicon Valley. I also have not seen any contacts, friend request, etc. to me on FB. I have a "net" I catch scam daters handles, e-mails, texts, etc. and file them so I thought it was from them.