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.
The account that is sending these messages is a fake account set up to send these messages in hopes that you will respond to them via text message. If you do, you will be sent a link to a pornographic site, according to a poster here who did text the number.
If you get a message with this number:
1) Unfriend the person sending the message.
2) Report the account to Facebook as either fake, spam, or scam.
In order to protect your information, as there is potential for identity theft as well:
1) Go to your privacy settings at the top of the page in the left hand corner.
2) Hide the following:
Your phone number
Your email address
Your date of birth (you can hide only year if you'd prefer)
3) Hide your friend list.
In the case of phone number, email, and DOB, there is no real reason this needs to be on Facebook. Anybody close enough to call or email you probably already has this information stored in their phone or email contact list. They probably know your birthday as well.
As for your friend list, I believe this is how this number is finding new contacts. Hiding your friends list will prevent the people you know from falling victim.
person's name is Nicole Caccavale said she added me becuase she liked my profile pic. Gave me this number 415-423-2158 i havent texted her and wont. the only reason i accept the FB request was she had a mutual friend. I was actullt trying to find out where the 415 area code is at and stumbled across this.