Why wouldn’t she?! She’s living the life of Riley and you’re completely enabling it.
You’re providing her a hotel with on-tap maid service and meals included, and if she chooses to sit on her arse all day and then go clubbing, there are zero consequences.
There’s a middle ground, OP, between accommodating her piss-taking laziness and entitlement, and kicking her out on the pavement with her stuff in a bin bag.
You need to stop. Everything. Stop buying her food and cooking it for her. Stop buying all her toiletries. Stop doing her washing and ironing. Stop cleaning up after her. Tell her she’ll need to budget to feed herself. Give her a monthly bill for electricity and hot water. Change the wifi code and tell her it costs money to use it.
If she doesn’t accept your perfectly reasonable request for a small amount of money to cover the huge amount you provide for her, then let her provide for herself and get a real idea of what it actually costs. If she won’t contribute to family life by helping you, stop helping her. Let her realise that if she doesn’t pick up after herself, or cook, or do her washing, it won’t get done.
Have a united front with your DH on this; don’t be the soft touch who always relents and lets her get away with it, because you’re not doing her any favours. You’re not helping her become an independent adult by pandering to her every need and tolerating her shitty attitude.
Then reiterate your original offer and say she’s got 6 months to get her shit together and start paying rent, and if she’s still a whiny, rude waste of space at the end of that, she’s on her own.