Transferring toddler schools to be with brother

So my daughter just started attending free preschool through the state 3 weeks ago.(she’s 3.5). At the time when I applied, they put my son down to (who was 6 months at the time) because infant wait lists are super long and they said he probably wouldn’t get placed until 2-3 anyway.

Well he turns one this weekend and they just called me that there’s an opening for him, but it’s at a different location than my daughter and it’s actually closer to our house. And if I don’t take it he probably won’t be able to get in for a loooong time. And if he gets in now he can stay in the program until he’s 4.

My dilemma is obviously they will either be at different schools or I would transfer my daughter (her location she’s at doesn’t have baby classrooms) which makes the most sense but I feel bad because she’s just getting used to her teachers and friends and I’m going to move her. But she also adores her brother and would love going to school with him and knowing he’s there with her all day. Am I a horrible mother for having to move her to another school? Because that’s what it feels like 😭