If the mum was me, here's what I'd have been thinking and how events unfolded from my perspective ..
(The OPs daughter, let's call her..) 'Jemima' has come to stay with my daughter at my house for a sleepover. Hope she has a nice time. Her mum seems a bit judgy so I need to make sure I do all the right things as a mum.
After playing with my daughter outside for a while, Jemima comes in with cuts on her knees. I think "Oh shit! What should I do? Looks sore, but I don't want to get over involved. My daughter will be embarrassed if I mollycoddle them or treat the like babies. Jemima probably doesn't want a friend's mum fussing. Mmm.. I'll just ask if she's ok and hand her some.kitchen towel to clean up, and then leave them to it. They are 14 so that's probably what they want."
Later - Jemima comes to see me and asks for plasters. I think, "ah bless her, must be bleeding a bit, good she's asked for a plaster", but "crap crap crap!! I haven't got any!! Maybe there's some somewhere in the cupboard." I start rummaging. As I'm rummaging, my nicotine patches fall out of the cupboard ('oh no!!') Jemima sees the patches and assumes they are big plasters - she asks for one!! I think 'oh shit! What do I say now?!!!' I don't want to say what they are. (Jemima's mum is not the kind of person I want knowing that I used to have a cheeky ciggy in the garden on stressful days) so I just skim over it - 'oh Jemima they aren't really the right plaster for you. Here look! I've found some smaller ones - 4 of these should do it'. Jemima says, 'but can't I have those big ones?' (I really don't want to say they are nicotine patches, so I just say "no, sorry they are for something else").
I'm feeling a bit flustered and then Jemima requests antiseptic wipes!! (Bloody hell!! I think we did have some somewhere a few years ago!!! I'm desperate to find them because I'm worried Jemima will tell her mother what a useless parent I am for not having a well stocked first aid kit, so I rummage and eventually find one wipe! ("Phew!!") Give the wipe to Jemima! :) Now I need a cup of tea!! The girls look like they want to go and chat etc.. and have some privacy, and I want to leave them to it, so i pop off to make a tea.
Next morning, Jemima looks a bit tired and complains her trousers have blood on because the plasters I gave her were not big enough. She has asked me to take her to buy some plasters in town when I drop her home (I'd agreed to drop her home as I didn't want to put her mum out. I'm a big softy like that. Don't like to trouble people. Always give the kids who visit a lift, even though most can walk. Jemima lives a bit further away though, so thought I'd offer to drop her back. Don't want to put her mum out as I know she's busy. Also don't want her mum to see my house! It's a bit messy today and I totally feel judged by Jemima's mum! So easier if I just drop her back!)
Anyway, on the way to drop Jemima home, I stop at boots. The girls jump out the car and go in a couple of shops together, boots and maybe the newsagent. Think they might be grabbing some soft drinks and magazines too. Hope Jemima's had a nice time. My daughter looks happy.
Finally drop Jemima home :) Hope she had a good time.
Later that night at Jemima's house .... her mum writes a Mumsnet thread about how bad and uncaring I am :( I did my best.