Thank you all for your answers/advice/contributions - can't say that I was expecting such a flurry!
We went to the gym this evening, and it was a new experience, to say the least. Clarification: I am a man - 41 yrs old, 5'8 130lbs, with decades of mid to long distance running, my daughter is 14, 5'7 "140ish" and she swims and plays water polo. She's been lifting weights 3-5 times per week since the summer of 2016.
Your answers were helpful, as I went into it not expecting to match her lifts. I didn't. Since it seems you all may be interested, I'll summarize my time as her fill-in lifting partner.
We did the bench press, and as she said she would, she did 3 sets of 10 with 145 lbs, which is a 45 lb weight and a 5 lb weight on each end of the bar, for those of you who don't know what that looks like (I didn't, to be honest).
Finding a weight for me took some trial and error, but I ended up doing a set and a half with 65 lbs (plus one rep in the "third set"). This is a ten pound weight on each side.
We also did bicep curls, in which I used a 10 lb weight and my daughter used a 25 lb weight. Then we did a handful of machine exercises that I don't remember all the names of - one was the shoulder press, a rowing one, one for triceps. We did (or tried to do) some pullups. We finished with doing a punching bag, which was maybe the most awful, because I have actually never thrown a punch in my life, and I'm certain I looked like a fool because my daughter was giggling the whole time as she wailed on her bag.
So to summarize, she was able to lift basically 2-3 times as much as I was on any given exercise. This wasn't necessarily embarrassing, as the gym was fairly empty of any onlookers, but it is definitely humbling to know that my 14 year old daughter is physically superior to me by such a wide margin. She definitely relished it, and our relationship has always been built on joking and teasing, so it would probably be unreasonable for me to expect her to treat this situation differently. So I'm sure that the "weakling" jokes will be flowing.
For those of you who will tell me I should hit the weights to not be such a wimp, based on the fact that this has never been something I've been remotely interested in, it feels like it would be strange for me start working out hard to surpass my teenage daughter in strength.