Siobhan isn’t the raven queen though. The Raven Queen is a collection of rumours and lies that are so widespread they got accepted as truths. Sebastien is much closer to who Siobhan actually is.
Lacer does make Sebastien run spells by him and tries to keep him out of danger. However, he knows that he was involved in something with Damien and didn’t push either of them on it. After the plot with Ana, he just pointed out he had forgotten about wand registration and committed fraud to cover up her lawbreaking. He trusts his apprentice enough to tell her secrets he was told in confidence.
He respected her refusal to use the tracking sheet and agreed he wouldn’t put her to sleep with a spell again after she made it clear she didn’t want him to.
Sihoban would not have gotten half as far as she has without the conduit he gave her as soon as he learned she needed one. Literally within minutes of finding out. It was also the extra exercise he gave her that she used to drive off the Morrows and reinforce the raven queen’s reputation in the first place. Not to mention how useful the output displacement has been for her.
As for her growth, there are four main reasons her will has grown and two of them can be directly attributed to Lacer.
First, obviously the amount of conflict and pressure she has been under. While this is obviously not caused by Lacer he hasn’t restricted her from leaving the academy or warned her to not to be involved in more plots like Anna’s. He has just warned her to be prepared and to be sure they are worth doing.
Second, is her split will letting her cast more. Again not caused by Lacer, the only interaction with this he has had is not spreading the information to try and keep her safe.
Third, the sleep substitution spell which gives her more time to cast in. Siobhan only managed to create this spell by using the book from the restricted section which Lacer got her when he found her trespassing in the library. He encouraged her interest in her research despite it being blood magic and actively helped her further it. The fact he confirmed it was a viable spell was also useful in convincing Lisa to seriously consider the spell.
Finally, her light refinement spell which he not only bent the rules to let her buy but also re-translated himself to make sure she could use it properly.
None of this is to put down her effort or say she doesn’t deserve this. She has worked really hard to make the most of her opportunities but it is worth remembering how much he has done for her despite her never asking him to.
Basically, I think her relationship with him as Sebastian is way better than her relationship with him as the Raven Queen as well as Sebastian being much closer to who she is than the Raven Queen is. He might not respect her as a peer but he does respect her and if anything trusts her more as Sebastian. Given how much space he has given her so far I doubt he will suddenly take away all her freedom, if anything he will probably push her harder to make sure she has more to back up her reputation with.
Also, I think the main thing everyone should have taken from the chase is that she isn’t his peer yet whatever she pretends.