Practical advice:
The most important part of sex is mental.
If a woman has a painful experience with size - she tends to decide that
"Big Hurts" and is therefore no fun.
I've been into stretching women for almost 30 years now, and have yet to find one who says "I prefer small".
Some admittedly are more enthusiastic than others, but within the size realm of the human penis it's really quite amazing what can be accomplished.
I am currently with the most serious (read obsessive) "size queen" of my experience and she is 5'0" tall and weighs 98#!
Her capabilties boggle the imagination (way past simple fisting),
so what is possible is really up to you and your partner.
As far as the "Baby" talk goes, #1, birth is a traumatic experience, most women have never passed anything larger than the "average" penis through their vagina, and then are asked to force a babiy's head and shoulders through it- besides the vagina, the mouth of the uteris has to dilate also.
Muscles tear, and usually some skin also.
Consider what would happen if the average person tried to do a gymnast's routine.
Stretching and exercise go a long way.
In the case of a virgin - intact hymans are actually pretty rare these days, many physical activities, tampons ,etc. usually rupture them during childhood or adolescence. I personally have never run across one, and I know for a fact that I've been with true virgins - so while a "bloody mess" is possible, it's not likely, being metally prepared is good, but being relaxed is better.
I strongly suspect that if you are getting your fingers in - it's not there, unless of course you can feel it.
Since you have already done some play with your girlfreind, I would suggest introducing a vibrator into your play, start with a smallish one, and then go larger as she's ready. Tease her slowly, avoid penetration until she is literally begging for it, then go slowly and work it in a little at a time.
Bring her to as many orgasms as she is ready for - don't force it, you are building her level of trust. Each time you play will build her trust levels and anticipation of your consumation, she will be more relaxed, and will be expecting it to be a pleasurable experience - usually a self fulfilling prophecy.
Something I also do with partners to get them used to the concept of size and being filled is to purchase some "Chinese Relaxation Balls" -
not "Ben Wa" balls, those are generally about 1/2" in diameter,
but the "Musical Hand Balls" usually found in meditation or chrystal shops. They usually come in small, medium and large, about 1", 1 1/2", and 1 3/4" respectively. I get the plain steel - one never knows what kind of reaction one might get to the paint on the painted ones.
In your case I would definitely go with the small ones.
Introduce them into play, gently pushing the in and having her push them back out.
The one caution here is that you don't want to get them in too deep where you can't get them out - she'll get nervous, tighten up and it will become an issue (They will eventually come out, gravity is our friend - but aga[in the point is to make the impression you know what you're doing)
If you are worried about getting them out, slipping them into a condom - which I would do anyway if I had a painted ball, will make it easy to push in and then give you a handle to gently pull back on as she pushes it out.
I would start with one, and then if she wants more, add the second one
(they usually come in pairs) If she enjoys all this, the next step is to get her to wear them for a period of time before she expects to see you.
Say if you have a date at 7 have her put them in as soon as she's off of work or school - say 4 or 5.
If that goes well, then extend the time, have her put them in at noon.
(If she can take that level of stimulation)
Well, I've rambled on long enough, If you have a specific question, let me know. I'm always happy to help.
Blackbeast