Legal Advice on the Status of a Will?

Here's the deal. I live with my father, who is 70, as a full-time college student in a house he bought from an auction in Florida, by his estimates $40,000. There is no mortgage he needs to pay off; he bought the house in full. The house was in terrible condition, but he & I (plus a contractor) put a lot of hard work into the house over the last 9 months. My father now estimates the house to be $120,000. Recently, he wrote up a will where my sister (who will be of legal age next year) & I would receive 2/3 of the house. The other 1/3 goes to a woman whom I'll abbreviate as MLB, who is 68. Why her? Well, according to my father, she has helped him out do menial tasks practically any able-bodied person can do. She now lives with my father & I as a co-habiting partner (though I refer to her as a lackey) in the same house my father bought and pays the bills for. She has no blood relation to my father & I, nor does my father & MLB intend on marrying. And MLB is not exactly the most kind-hearted woman you'll ever meet, either. What's most damning is that he wrote up his will with the intent that neither party (myself, my sister, and MLB) can force one or two others out of the house's value. I don't intend on living in Florida for too long, just enough to get through college and maybe a few years of work experience. However, my sister & I - as next of kin - should have a say-so about the minority owner and her slice of the pie. MLB not only has her own family, but they live only 1 hour away. Ridiculous, right? And besides, I (along with my sister, presumably) don't want to sell my portion of the house one day and give full ownership to a woman who has no more of a right to the house than you do. I wanna cry an act of collusion, but my father does all but listen to my pleas. I love my father. I don't hate MLB. However, upon my father's ping, the house should be just mine and my sister's. But, if he wants a way to divide my family up a lil' bit more, he's certainly doing so. Any and all legal advice regarding the status of his will is welcome. Thank you all, in advance.