Oh gosh, I'm sorry to hear this. It is always hard for parents to face when their child may have a challenge or issue. There is a really wide range of normal with kids, as you probably know. And some develop earlier and some later. However, there are definitely red flags here. Not pretend playing is a sign. Does she ever pretend to be a kitty or a doggie or a baby and crawl around? Act anything out? Engage or interact at all with siblings or you guys? Can you give her any commands that she will follow? Such as, please bring me X. That is age appropriate. Some kids can do two step commands like go to the door. Stop and turn around in a circle. But for her, I think I'd start by just a simple command.
There are different parts of speech. There is receptive--- taking in what people say to you, organizing it, understanding it. Expressive--- thinking of how to respond, organizing thoughts and words, knowing what you wan tot say. And articulation--- actually saying the words. If any one of those three is off, then kids have trouble effectively communicating.
The thing about autism and speech delays and sensory integration disorder (which my son has) is that you can SO help a child if you do early intervention. My son started seeing an OT at 4. He was a little behind but it was earlier enough we could really dive into helping him. He's now 14 and functions fantastic. No help at school, good grades, plays sports, is social but we had to work to get there. SIX years of occupational therapy!
But is hard if your boyfriend is not wanting to look at this. I think you could say that you are simply worried about her. You want the best for her and that maybe she needs a little help. Does she attend preschool at all? My sons at 3 did two half days a week of preschool. They were not in daycare but did this school and that was a great thing because the teachers wouldn't LET me deny there was an issue no matter how much I didn't want there to be! Another avenue is to ask her doctor. But I would just be sincere and honest and tell him you are not criticizing his daughter. You want to HELP her! Because you care.
Let us know how things go!!
It's impossible to give a diagnosis like that. But some family has lots of late talker and they end up just fine. So I understand he may thing his daughter will talk late as her brother did. But... I think he still should have her testes by a professional to see if anything is wrong. He really has nothing to lose, if she is fine, great, if she needs some early intervention, the best would be to start asap anyway. You both can already help her with toys, play with her, show her how to pretend play with a doll and see if she will play appropriately after you show her how to play with toys. Talk to her a lot , to help her language skills. And teach her to follow instruction etc... does she point? Does she wave ? If not, teach her. ( you or him or someone else) Some kids just need to be teached first...
My dad talked at 3 and ends up fine, his uncle talked at 5 and ends up fine. But my brother talked at 2 and a half and is on the spectrum so you never know...