Hey J.,
If this is just one event, and you have not left out A LOT of information about why you would think autism, then you probably are overreacting. Autism has a very specific range of behaviors that manefist in social, langague, communication and sensory issues that are beyond the typical behavior range in their scope, frequency, and intesity. Autsim does not pop up at one event.
I am one to tell Mom's to trust their gut, but you seemed very focused on yourself and your frustration with how the birthday party made you feel, and how angry you are with your husband for not agreeing with you. I think for anyone to take you seriously, you are going to have to take yourself and your emotions out and be more focused on what is bothering you about your daughter. How you feel about it, and how your husband is not seeing this too is a totally seperate issue.
If you have a lot more to add that makes you wonder, and you need someone to bounce it off of, repost with a clearer picture of what you see and those of us who have autsitc kids can tell you what we saw and guide you on how to find resources to find out for sure. What bothers you about her speech, exactly? The majority of speech issues are not autism, but you should never delay language intervention, so please be more specific so that you do not loose any time on that.
And just a personal note, when my autistic daughter had meltdowns at a public outing, we left because it was best for her and it was considerate to everyone else, but I did this with my typical kids too. It meant missing things that I would rather have attended, and it meant that I was disapointed. As Moms, we have to put the focus where it belongs and this is one of the sacrifices we make, to go home when any child's behavior is unpleasant and they cannot get it under control. I can tell you from experience, having a typical kid means letting go of what disapoints me and moving on, and having an autistic kid means doing that a lot more than I ever imagined.
Post again, especially about the speech.
M.