My girlfriend is extremely delicate, I need help

So, My girlfriend is a very special woman believe it or not she is a 32 years old virgin due to obesity and low esteem, plus she has been always looking for real love and even if she had pretenders, they didn’t want her truly. So she has some mental and physical issues regarding sex, I am not the most experienced man and I have issues of my own, so this is even more difficult than it should be. So, I bought a vibrator for us to play with because she wasn’t ready for penetration, but it seems like she is somehow allergic to vibrations… yes, vibrations, so every time I use the toy on any part of her body it starts itching. And then when I try using my fingers in her intimate place, it usually gets irritated and swollen, and we had tried many different lubricants. The only way I have managed to not hurt her is by using my tongue but even then, I have to use lubricant, and I can’t take my time to do it because if it takes way too much time, like 15 min it will get irritated… Now, when I first tried to use my fingers it seemed like her entrance is too tight, and my hands are small compared to other men, only once I managed to get her really aroused and I was able to insert my index finger, I am not sure if this is normal but my index finger is like 9 cm long and I was able to touch her cervix (not that I was trying to do that)… again this worries me because if I use my penis it will be too painful for her (even though my penis is normal/small sized, it is bigger than my fingers) and as time goes on it is getting more and more difficult to practice sex, for example: at the beginning, she loved to be grabbed and sucked hard on her breasts but now she found it too harsh, last time I touched her like for 2 min using coconut oil, it got really swollen… So I don’t know what to do… she asked the doctor, but to examine her vagina they need to introduce a device inside her vagina, and she feels like it’s wrong to use a device first as she thinks it should be a penis first…