I'm married and was in the same situation a few years ago. My SO moved with me - she didn't wait. There are some positives from your SO not being able to move out until later in the year.
The first 3 months of a job can be tough. Adding a new location means you have things changing at work and at home. You're adjusting to everything. It can be easier to do this when you're alone since you can de-prioritize certain things. For example, you might have to stay late frequently in the beginning so you can onboard faster. It's easier to do this if you are on your own and don't have your SO who needs support because they are also adjusting to everything new.
When this situation happened to me, I realized in the first 30 days that the job environment had been totally misrepresented and was horrible. We had moved from a low/medium CoL area to a high CoL area. My spouse had moved with me and was looking for work. The move had been tough because we had to downsize in a major way. We were tired, frustrated, and struggling to wrap out minds around the vastly increased CoL, even though I had gotten a solid salary increase. Then I came home and said "This job is awful, I made a mistake." Since the company had moved us with a clawback, the money had already been spent and we would have to pay it back if I left.
We both realized that moving together had been a mistake. I had to be onsite, but the company that hired me had given me a year to move my home. I could have rented a studio apartment and moved/purchased just enough to live a basic life. Then I could have easily switched jobs or moved back without thinking about the clawback or all the energy we had put into moving. I ended up staying in that job until the clawback amount dropped enough that we were okay with paying back a portion. I hate being away from my spouse, but what happened was far more stressful for both of us.
Don't take what I say as a warning about your job. I provide my experience to say that there are positives to moving alone and having some of that risk mitigated by your SO having a secure base where you are now. If you are committed to each other you'll be fine.