Hello and welcome! It's such a worry when we go away isn't it. I was going to say that ideally, it would be best for her, to leave her in her lovely cage in her familiar environment in your home, and have someone go in once a day to put food and water out. That is all that is needed - just someone to go in once a day around the same time to put out food and water (and check the house is ok). But then you said it was over Christmas! And yes it can be difficult to find someone who would do that over the Christmas period possibly. If you can find someone, that is the best option if it's only for four days. If it was two days you can just leave them with extra food and water but anything longer than that, someone does need to go in. It's not just to put the food and water out, but also so the hamster senses someone is there once a day and doesn't feel scared or abandoned. It's reassuring for them.
Is your boyfriend's house near yours? As in would it be far to take her for a few days? Does she know your boyfriend/familiar with him? If so then that might be an option - to take her to your boyfriend's house for a few days. As Rainbow says, you'd need something bigger than a crittertrail though.
You'd need a pet carrier for the travel period (it's not safe to leave them in a cage while travelling as they could get thrown against the side and everything spills or falls over etc with jolts). So it would be transporting her there in a pet carrier you can secure in a car for example, and taking a holiday cage with you. Plus taking bedding, familiar toys etc, from her main cage, to put in the holiday cage (that helps them settle a bit if they have their familiar smelling things from their main cage).
I actually bought a smaller cage just for holiday type purposes. It's small enough to transport easily but not too small for a hamster - it's about 70cm by 45cm and quite low so the base sits inside the barred top and it makes a small package for transporting somewhere.
Are you in the Uk? The Ferplast Duna Multy would make a good temporary holiday home. Or a bin cage as Rainbow suggested (the ikea samla 78cm bin would be ok). However a cage like the duna multy would be easier to transport with you as the top sits in the base.
I would find out about petsitters though. I have a petsitter who comes to the house. She doesn't charge too much and does this all the time so as it's a job a pet sitter might not mind doing it over Christmas!