I think it's important to look ahead at things too eg...DD has maybe a good teacher responding well in supporting her at the moment but as your DD is getting older she will begin to be aware of her differences, be presented with more expectations and be expected to manage more responsibilities, etc, self management, organisation of herself, socially be able to manage and communicate with peers, etc....that she may not always experience a teacher with this understanding and experience in supporting these things enough for your DD (some teachers are just not equiped to really be supportive and can cause no end of issues as a result.) That her peers will recognise 'differences' and this can create many issues too (bullying, being left out of things, struggling to maintain friendships, etc possibly being isolated and becoming withdrawn as a result), all of which will impact on her potential to learn well, be able to manage, etc
Knowing a SS has the expertise, experience, children of more equal footing to DD, interventions, social skills teaching, integration and encouragement in all these areas, makes a great deal of difference.
I'm all for 'inclusion' in MS but there is a huge area where some children simply cannot manage and be supported enough to thrive in MS and can hinder them reaching potential as the MS environment becomes more a matter of just coping and management of themselves and of the staff doing enough to manage things...it's very difficult to see a child thrive at all within this environment and ever grow their wings to their potential.
It's about whether you believe your DD will thrive well and manage well in MS or if your believe she will need SS to be successful and reach her full potential with the right supports and interventions available to her from the get go iykwim.
I hope this is some help to you...there is so much to consider, especially going forward to your DD getting older and what this all means for her as her understanding increases and gaps may begin to grow between her and her peers, etc....and how a school will support, assist and intervene positively with these areas of need as well as good supports and resources to aid her learning and whether use of other equipment will be needed....eg if your DD needs a laptop for written work or visual needs, etc...will she be able to sit and do this if she is 1 of a large class needing this resource to learn and how will she manage this difference to herself? Will she refuse to stand out in this way, be 'different' and cope well with this, the impact this can have between her and her peers, etc. If she requires extra support and 1:1...will she be happy to leave her class regularly to have this help or will she not want to miss class things, have to leave class...again the 'differences' becoming apparent and the gaps growing, etc
At an SS school these things are generally supported in class, the group or class will be smaller, probably of more equal abilities and needs with her peers, not having to leave her class as it is delivered to the group appropriately, maybe all using resources, laptops, equipment, etc. Many of these supports for learning are 'in-house' which can limit the time out from school too. Specialists are 'in-house' too so she isn't losing school time and you aren't dealing with as many appointments, etc.
I don't know how helpful I am being but these are considerations I have had the experience of dealing with, after the fact for my DS and the impact of many of these things has taken a huge toll on things for my DS. Mine are all in hindsight so I thought it may help to share this and help you look at this perspective for your DD...I hope it helps with your process and moving forward