Your question brings a variety of thoughts.
1. you say the best quality you have was to big for the beginning. A thought she's a girlfriend, New? Old? either one you already have a stash of dildos. What might she think of that., that you use them on yourself, that you used them on how many others before. have they been cleaned.
2. maybe she's just not into using a second hand dildo. Try taking her to a seller of sex toys and invite her to pick one herself. If she will not drop the subject. let me share some observed thoughts. There were women in the swinger groups we joined that would freely take another man's cock that would not use a dildo. They obviously had some mental barrier about doing that.
3. type or quality as you call it a possibility. Those hard ones that look and feel like plastic are a bummer. Those that are not as rigid and are flexible, feel and can be bent and look like a real cock are far better. You say heat it up, that may work and it can be done a heating pad on low will do the trick. Get it too hot and it's a mood changer, you might end the night alone.
4. on a personal note maybe she just prefers the real thing. I do and only used my heated dildos when putting on a show before the sex started while doing bachelor party or other all male group party. I did use them if i was still worked up and the man i was with ran out of energy or desire.
If your friend really gets into sex you might try using a dildo after you've had a session where she wants more. I know of men who've both gotten the lady to use them and even get them interested in another guy or two by suggesting it would be better if it were real.
). She always saying she prefer real and do not like fake things, she do not masturbate and do not like that, only once agreed to use dildo in foreplay.
