1. Why don't you make some recordings of females speaking the sentences instead of writing them out in text?
That would feel a lot more realistic, and it wouldn't even be very difficult to implement

2. Later you could implement Speech reconnection instead of typing for when the user speak to the girls

Because voice actors cost money. Especially ones that are any good.

And you have to nail down your script beforehand, which takes time and effort.

It's not a terrible idea in general, but it's probably premature at this point.

What would be better, if possible, is to get a really good TTS engine. I don't know that any good enough actually exist, but it would be more flexible than prescripting dialog.

i think they are already doing that to version 4.0 that is why it is taking so long because they are getting ready for 9.9 i think this will be last engine they make

I think this would be a great idea and I'd even be happy with an OK quality TTS system over reading the text.

Is there some way to incorporate the speech to text system built into Windows 10 to talk to the girls and have it auto type? Just a thought.

This may be a premature thought. But it just came to me when you asked if the Windows TTS (or any other TTS software) could be used to type for you.
I have done no research into this so take it with a grain of salt but things like AutoHotKey and AutoIt can interact with most windows on the computer.

So, if you opened notepad and the TTS software, you could have one of the two scripting languages grab the text generated and copy it into the game.
The biggest hurdle with this that I can see would be that the game window has to be active for obvious reasons, but I believe notepad would have to be active
for the OS to type into it.

Then again, it might not need any of that. maybe just having the cursor blinking in the chat window before attempting TTS is sufficient if the TTS software just
simulates keystrokes.

testing needs to happen now....

I haven't actually tested any of this. got sidetracked with another project... ( I have alot of those at any one time )
but as far as generating voices for the girls; given the right tools, anyone can change their voice to sound like dozens of other voices. This includes going from male to female. I don't mean just having good vocal control, though some people are very talented. I mean just fine tuning the pitch and speed would help quite a bit. You could even dig a bit further and start adjusting very specific frequencies within the range of your voice to change things and make it sound even more unique.

If anyone around here was good with those tools ( I know of them, but not so much how to use them effectively ), then any of the guys (let's face it, the majority of us are male. though I am sure there are a couple females) on here could speak the words needed for one of the girls and then have it changed to sound genuine. The biggest issue with TTS is that they can't accurately inject inflection. with people saying them, that wont be a problem.

not sure how someone would feel knowing the voice of the girl they are interacting with is their own though.... lol
more thoughts on the subject since I had them....