Am I wasting $ on BR decor?

Currently both girls share a room; DD1 loves being around her baby sister.  However, DD1 has woken up several times each night crying in the past 2 wks also waking the baby. No idea why (yet).  Sometimes, we move her in the spare bedroom to sleep.  When we ask she prefers sleeping in her room w/ the baby.  To make the transition more fun, I thought of decorating the spare room w/ her fave princess'.  I picked out new sheets, curtain,wall stickers,etc...about $150 worth.  Should I bother?  I could always move the baby into the spare room.  I'm just thinking ahead.  Eventually DD will outgrow her toddler bed w/ the matching sheets.