Spoilt is not caused by letting kids have the things that express themselves or 'fit in' but rather by denying them what they see everyone else has, they then spend their life chasing what they feel they should be getting because it's 'unfair' to have 'less' in their eyes.
Is it now?
In the case of the OP, the dd isn’t going wo when all her friends have whatever. She is getting DIFFERENT things. So she might not have the latest Disney towel but she has activities right left and centre for example. Activities that she enjoys.
Like anyone else, if she had ‘what everyone else has’ then she wouldn’t be able to have all the things that ‘everyone else’ doesn’t have either. Is that good? Is that a wise choice to teach a child to just go with whatever other people are doing with no regards for what SHE likes doing?
I personally wouldn’t want to teach my child that tbh. ESPECIALLY if she is finding hard to fit in (which the OP never said - that’s other posters’ conclusion).
FWIW buying the towel might make her happy (for a bit) but it won’t help her ‘fit in’. Fitting in is about more than a towel, it’s actually more than the obvious material thing that children (and adults) have.
A child that doesn’t fit in shouldn’t be taught to do whatever it takes to fit in, but the latest iPhone because everyone else has one or the Disney towel. A child like that should be encouraged to find their own friends, those who are in their wavelength. (Probably by encouraging those activities others don’t do). They should be encouraged and supported to build up their self esteem. They should learn about themselves and to be proud of who they are.
Believe me, as someone who doesn’t fit in and whose dcs have struggled to fit in, it’s not about the Disney towel. It runs much deeper and is much better handled by build self esteem and being round of who they are than by buying stuff that they only care about because that’s the stuff others have.