you can set your facebook settings so that only you and those on your friends list can see your page. that is how my private, family and work facebook setting are. you can also set your facebook so that no one can search for you by using your email, phone number nor address.

when you have all your facebook settings set if someone happens to find you or they have already found you and tries to see your facebook page all they will see is your name and a statement that in order to see this facebook users profile and all they have to be on your friends list. you can also set your facebook settings to whether or not you want non friends to send you messages or not. you can also set your facebook so that no one can send you a friend request. you send out the friend requests to those you know rather then people sending you the requests

my suggestion if you dont want this person seeing your facebook, stalking you on facebook review your settings and reset them to friends only and close out messages for non friends.

you can also use library or other public computers rather than using your home computer or cell phone to access facebook.

as for her snooping on your cell phone thats easily fixed too. when ever you send a text go into your sent box and delete the texts the same with those you receive. if you find you want to keep a text get a free yahoo email account then forward the texts to your yahoo email. this way you will have the texts on yahoo and not on your phone where room mates friends and family can accidentally or purposely snoop into your phone for them. dont attach your cell phone to yahoo. just memorize the email account so you can send the text to yahoo and then delete them off your phone.