Confronting Fears

I have a friend who is a wonderful person. She is actively involved in her Jewish community, and hosts many large gatherings, bringing people together often. We were friends a long time ago, and when we saw each other again after many years, she instantly welcomed me back into her life, and I did the same to her.
I noticed one time when I was at her apartment on a Shabbat that she puts pre-cooked food in the oven on Shabbat. I noticed this, and felt somewhat awkward, since I've learned that one is not supposed to return food into the oven on Shabbat, even after it has been cooked, but instead, we are to cover our flames and knobs and only then (and even then in a very limited fashion) can we put food onto the fire on Shabbat.
I left her apartment very troubled, since I was so happy to have finally reunited with this wonderful human being, but was devastated to find that there would be conflicts of interest every time she would invite me over (and she would, often). I talked about it with some friends, and some of them insisted that she must have a Rabbi's permission to heat up food in this way. Others said, "ok, but that's what we do when we're halakhically observant. We can't eat at everyone's home." I went back to her house one time and ate there again, but became extremely uncomfortable about it, and I finally brought the question to a Rabbi. He told me that he did not see how this could be allowed, and that maybe after it's been heated up, I might be allowed to eat it so as to avoid embarrassment, but it was generally prohibited, and I could not go back, knowing that the food would be heated up that way.
I was saddened by this answer, although I found the Rabbi's efforts to find loopholes heartwarming. I continued consulting with other people. I spoke to a friend of mine who was in Rabbinical school (but has since graduated) and he told me that I should explain to her my position, and see if she wouldn't change the way she heated up food when I was there (and maybe others, too) in order to be accommodating. I thought the idea was a good one, but the idea of confronting someone about a religious matter-- and so personal, too! was terrifying. I didn't want to insult my friend, and I didn't want to make her think that I didn't want to be her friend anymore, if she chose not to take my advise. I can imagine someone trying to make me heat up my food on shabbat in a different way, and being terribly offended and personally insulted.
i avoided the conversation for a long time, and this week she invited me to Friday night dinner again-- on facebook. I had no other plans, and I was actually looking for a meal. I told her that I would love to come, but that I wanted to talk to her about something, and when could i call her? She called me a few minutes later, and asked if I could talk then. I told her I could, and where was she? I thought she might be at home, and then I could go over and talk to her in person. I feel better with confrontations in person, for some reason.
She was at work, but had some time to talk, as she had not taken a lunch break. I lunged in. I said, "This is a kind of sensitive issue, but I want to talk to you about how you heat up food on shabbos." She repeated, "How I heat up food on shabbos." I explained why i felt uncomfortable with the way that she heated up food, and she said that she doesn't leave the oven on in the summer, so that wouldn't be a problem, anyway.
At this point, I started regretting the whole phone call, since the immediate issue was no longer present. But she continued to say she's never heard of this issue before. She asked me a couple questions about the rules, and I tried to answer them. But I was really not thinking about the rules. I was shaking, worrying that I had insulted my friend. I mentioned that to her, and she said, "No! Are you kidding? I'm so glad you told me about this. If people are uncomfortable, I want to fix that. I need to look into this some more."
I was so grateful to her for responding in this way, and I told her so. I think that she thought I was a little extreme, getting so worked up about this, but there I was, exceedingly relieved by the way that she had responded. She called my back a few minutes later, and told me that she had spoken to her father, and he didn't know where she got the idea from that it was ok to put food into the oven on shabbos. She wanted me to know that he was grateful to me for pointing it out, and that her roommate had heard and she was also grateful.
A couple of thoughts: I learned from this experience that I should be less scared to confront people if I want to address an issue. Some people can take more than others, but as long as it is done in a respectful fashion, it seems that communicating issues is a good thing all around, and can even lead to resolution.
I hope that this story can inspire me and you all to speak up and not be so afraid to share your concerns with people-- especially your friends.