Legally be put on deed?

Ok, here's a sticky question. My boyfriend owns his home. He is the ONLY one on the deed. However, his ex-girlfriend of 15 years still lives with him- and refuses to leave. She feels that she is owed half of everything because they lived together for 15 years- only half of which was in that home.
They live in California. So, I did some research, and California does not recognize common law. However, she has a lawyer who insists she can get her palimony based on Marvin's law. So, we understand that, but here's the newest dilemma the ex-girlfriend has posed. My boyfriend hasnt put the house up for sale, because the market in our area is incredibly low, and with all the mortgage problems California is having, nobody is buying. The house next door has been on the market for a year now. Anyway, she came home yesterday and said because he hasnt put this house up for sale yet, that her lawyer is going to put the ex-girlfriends name in the deed so that SHE can sell the house herself.
WHAT THE HECK?! Can the lawyer legally do this? My boyfriend is NOT giving consent for this to be done, nor is he going to sign anything. But the ex-girlfriend says she doesnt need his signature. She claims the lawyer can get the girls name put on it without my boyfriends consent. Is this true? To us that's against the law. I dont know what scheme the lawyer has come up with to do this, but supposedly today the lawyer and the girl will be contacting the bank and getting her name put on the deed.
This girl barely makes any money. Maybe $400 a week. Does not file taxes- yep you heard me right, and has no verifiable income. She is a "travelling" manicurist. She has no business license or cosmetology license. So, how could she even get put on the deed to begin with? Don't you have to make a certain amount to even be considered for the loans, etc?
I guess I'm more bothered by the fact that they are going to go behind is consent and try to get her put on the home deed. We're worried because we dont know if this can really be done. He cannot afford an attorney and asked me if I could do some research for him today while he's at work.
If this girl gets put on the deed, she plans to put the house up on the market immediatly. He owes "x" amount of dollars, and if the house sells for way under, which we are almost assured it will- if it even sells- then he will owe money. So, where does she think that she will make any money from the sale??? She has it in her head that she will sell the house, and take half of the money and then leave him alone.
I am almost sure that she cannot get her name on the deed, but I would like more opinions on this matter. If she somehow does get her name on this deed, can my boyfriend take her and the lawyer to court or something for doing this without consent? HELP please. Somebody offer some tips, solutions, opinions, etc. Thanks so much for listening.

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She cannot do that, and the lawyer cannot either.

If she has any rights--and that is debatable --see the following:

If two or more owners cannot agree on what to do with a piece of property they may petition the court and the court will order a sale or refinancing etc. so that the one or more may get out of the property obligation and/or the other(s) may keep it etc.--it is often done-- (This is true in some cases even for equitable owners that have paid various amounts etc., but for various reasons, may not be on title.)