Family Ties

My dad has a little problem and has been married three different times, not including his 2 year long engagement with my mother. I love him to death, but growing up, it has been slightly difficult with all of his different women and my different step mothers. For the most part, I got along really well with everyone and didn't have any issues. His current wife, Tammy, is a different story. It's not that I don't get along with her, but we do not have a close relationship by any means. They have been married for about two and a half years, so I was seventeen when they got married. I know it would be difficult for her to try and build a relationship with my because I am not a child anymore, but Tammy makes no attempts.
Tammy works at my dad's dealership but she only comes in occassionally. When she does come in, she never says bye when she leaves. She never says hello when she comes in. She doesn't ever talk to me or to try to make an effort and she only talks bad about my dad. I wonder if she is jealous about my relationship with my dad? It makes me nervous that maybe Tammy is in the marriage for all the wrong reasons. My dad just turned sixty four and has heart problems. Tammy is nearly twenty years younger than him and no longer has to work that much. She can go to the barn and ride her horses and my dad will support her fully.
I don't want to sound like I am complaining, and I don't need Tammy in my life. However, if she is such an important part of my dad's life and doesn't have any kids herself, I would think she would want to try and build a relationship with me. She doesn't try to communicate with me at all and is very stand-offish.