Yes they can, assuming that they’re transferring the money from a UK account, there’s no charge for either of you.
If you need the money sooner, you could use Monzo.me (iOS overview & Android overview) but if you have the option, a bank transfer saves Monzo money 
Just bear in mind that monzo.me has limits so they may have to make several (quick) payments & you can only receive so much through it each month etc.