2yr and 3 yr old sharing a bed?

About a month ago my mom and I took my nieces, my mom took the 2 older ones (6&3) and I took the almost 2 year old. My mom cannot handle the 2 yr old and the 6 yr old can’t wait for her to leave so my mom is bringing her to stay with me to try it out for a few weeks and then deciding if I’m going to keep her or send her back to my moms. Is it ok if they share a bed? The 2yr old right now has a twin size bed. (They’re both girls)

Any other advice is appreciated. I don’t have any kids of my own and still don’t know what I’m doing lol also they both seem to have nightmares nightly and wake up crying talking about a monster: