Can't you contact OT and tell them you need a Major Buggy, they have a high up seat and would be great as Tegan would able to interact a bit more when out and about....also she can talk can't she, so that's a plus as she'll have that interaction with people.
I have had an isolation issue and have done so since my eldest child started showing signs of varying problems....he started off with no speech and ADD diagnosis, which then once heavily assessed was found to be Autism of the severest scale, he is totally non verbal....(I will never hear him talk or say Mummy....

), is Globally Developmentally delayed, has stomach problems which cause all sorts of eating problems, sleeps badly, uses a wheelchair sometimes, he can walk but has sensory difficulties and no awareness of danger, is still in nappies and will remain so...and is now also being tested for Prader Willi syndrome and underdeveloped reproductive organs....
I've experienced the comments and the stares with my son and I still do....and I imagine we will always have that....but will say that once you get a wheelchair you'll find people tend to see that and not ask...as it becomes apparent there is a disability, so you'll find that makes everyday easier to bear.....this will sound a bit weird, but a physical disability won't be questioned as much as a mental one as it's visual to see, iykwim? Sometimes people unfortunately still just think my boy is wild/feral/naughty/I'm a terrible parent...but sod them...If they don't ask, I don't volunteer any info....plus it's way too complex to go into!!
As a family we still have a lot of difficulties, with Ellis we can never predict what will happen and we do accept invitations out but they are never "normal"...we will go to family parties/occassions and one of us will sit in the car with him whilst the other go inside the party and we take it in turns...sometimes he will be social and other times it's a complete no go....it's just how it is...at least with Tegan she won't do that...she looks very sweet!!!
What I will say is LEARN TO DRIVE....do it for Tegan, it will open up a world to you and give you freedom...and her a chance to go out and have fun. You can contact various place like Family Fund and apply for free driving lessons and once Tegan is three you'll be able to apply for DLA Mobility and I am certain you'd be on the high rate because of Tegan's disability which would enable you to finance a car.
It's hard, I know....but you have a lovely little one there and it will get easier as time goes on and you get the chair and you start to become immune to people's comments/questions... just enjoy her cause she's lovely!
Don't hide yourself away, you need to get out and don't worry about what others think!