<human>: Give me a shortened version of the text

I [25/f] with my boyfriend [27/m] want to move in together soon. I live with two roommates [25/f and 28/f], and I love the place where we live. I don't want to leave it, and my boyfriend has no attachment to his current apartment. He spends a lot of time at my place, is friends with both of my roommates, and he'd enjoy living there as well, except... it would not be big enough for 4 people (only 1 bathroom), and I don't want to continue living with one of my roommates. 

Let's call her Sam [25/f]. Sam is not very tidy. No one is perfect, but she is a *lot* messier than I can handle: dishes in the sink for days, leftovers clog up the fridge until someoneELSE throws away the moldy mess, hasn't swept or wiped a counter top since we moved in.

The other roommate is great, and both my boyfriend and I can co-exist with her and her living style (messiness level, hours she keeps, etc). 

**Is there a polite way to ask Sam to move out when the lease ends?**

All of us are friends, and my two roommates were friends with each other before I met them. My only other tactic is trying to encourage her to move in with her boyfriend (she spends 2-3 nights a week at his place already) if she brings it up.

I haven't told them I'm moving in with the boyfriend, if that detail matters.
<bot>: I want my boyfriend to move in with me, but also ask one of my roommates to move out. Any way to handle that sensitively/politely?