She's past her prime, aka Spinster, and wants to go back in time to relive her 20s when she had a lot of attention from men. I'm guessing your mom's friend is either divorced, widowed, or she waited too long to get married by wasting her youth partying with "hawt" guys that didn't want to get married. A 40 year old man, as long as he's not fat and makes a nice income, can marry women half his age. However, women above 35 are off his radar. Her only option is to marry a man with a low income, or a man that's 50+. She's probably bitter because the nice men she ignored in her 20s, are ignoring her now. She's wondering, "Where are all the nice guys?"
Maybe she's against marriage and wants you to be a party girl? Might be she's unhappily married with kids and wishes she was you? Yes, guys don't act like this. Your mom's friend seems too emotional and might be experiencing a mid life crisis. You know: "You GO GIRL! The new 40 is the new 20!"
This reminds me of the film 'Single White Female' How creepy..maybe there's something she admires about you and she's just trying to emulate it because she's insecure?
Could be she has a crush on you, that does sometimes happen you know, or maybe she's just subconsciously trying to recapture her youth.