I'm sorry but this is all very bizarre. The OP is paying a sum to a large corporate for the use of facilities as per her consumer contract. Management needs to organise things such that their customers are able to receive the goods, facilities and services they have contracted for during the times they are contracted to provide them.
No one should therefore be taking those facilities out of action, either through use of harsh chemicals (should be done out of hours) or to expedite their ability to meet their contractual commitments (ie all showers to be cleaned by 1030 concurrently with gym usage) due to their contracted working hours. Employees or subcontractors who provide services which take these facilities out of service should be contracted, and paid a premium in my opinion, to work outside of opening hours.
Why should the OP inconvenience herself so that the owner and shareholders of the corporate can take a fatter dividend than if they were employing and contracting for services properly, and paying accordingly, to deliver on customer expectations?
It is not about the human rights of the cleaner vs the ops, "menial" jobs, entitlement etc. It is about business management. If she doesn't complain, how will the management know their customers are not happy with the trade offs the management are making when running their business?
OP, you shouldn't complain about the cleaner, you should complain about the situation. The cleaner is probably contracted to do what she did, or needs to do it in order to meet the terms of her contract/objectives, and that is what is unreasonable - and that's a management responsibility.