<human>: Can you provide a brief overview of the text?

I have been exclusive with my girlfriend Emily (not real name) for about a year. I think it's a strong relationship  and we are pretty sexually active.

Recently she asked me to wear specific clothes before/during sex to create sort of a role playing situation. These include one specific outfit (think sweatshirt for a specific university), eyewear and hat. I asked her why she wanted this and she just said it was a fantasy for her. I thought this was kinda weird but I didn't want to shame her over it since I have requested some unusual stuff in the past. 

So I am hunting down these required outfits for the last few weeks. I went over to my gf's family's house for new years and saw a picture on their wall of the family back when Emily was quite young. I should mention at this point that Emily's dad passed away from cancer when she was a teenager, so this picture must have been taken before that. It's was a vacation picture and in it her dad was wearing (almost) the exact outfit she requested for me to wear during sex. I didn't know what to do so I just kept my cool through the party. 

Since then I have been unable to get over this, which may reflect poorly on me but whatever. Although it is really gross for me to think that she is fantasizing about her dead dad I can't think of any other explanation for all of this behavior. At the same time, I don't want to outright accuse her of anything because it is a pretty serious issue if true and would be seriously awkward if not true. Like: "Hey, are you getting off from memories of your dad?" would be pretty offensive.

Should I bring this up to her? Is there some explanation or information I am missing to make this make more sense? How should I proceed?
<bot>: GF asked for me to dress in a specific way during sex. I found a picture in her mom's house showing her dead dad in the exact same outfit she requested. Should I bring this up to her? How?