So I saw this thread and made an account just to reply because I just had this problem the other day and looking for a solution I found this thread. I played around on the game a bit and found a better solution that doesn't involve losing anything that I wanted to share..
So at first I tried to make the mother move out by switching homes and having a friend invite her to move out (as she was a single parent when she took the vacation). I figured if I moved her out and back in the game would realize WAIT she is back from vacation! That didnt work. The game kept freezing. So since I couldn't move her out organically I went into edit town and split the house. I removed her from the house and placed her in a random neighbors house. I found that in the neighbors house the people she lived with had the option to go to University.
I then went back to my original house and tried to send her daughter to University!! Seemed like the glitch was connected to the lot rather than the Sim. Still said the adults were on vacation! So I split the mother from the other house, put her back in the original house then using edit town moved the daughter onto another lot.
Lo and behold the enroll in university option was there for her! Yay! I had her enroll and she now has a degree in communications. When she got back from Uni and I moved her back into the original lot using Edit town the option was still there and everything was un-glitched as far as that is concerned.
I know this is 3 years too late for the OP but hope this helps someone.