I am the mom of a compulsive gambler. Good on you for coming here and trying to get help/support. I can tell from your post that you have all the “normal” feelings of being a family member of a CG… anger,fear, confusion and probably the biggest one- FRUSTRATION!!
This is a very tough and unrelenting addiction. Once it has it’s hooks in someone it is not an easy journey for anybody involved. While your mom will never be cured it can absolutely be controlled. The hard part for those that love her is that only she can get herself to that point.
I think it is time you shared this with her partner. This is too much for you to look after and it’s not fair. Addiction thrives on secrecy so if you can talk with your mom and her partner and come up with a plan to protect her money that would be a great start.
Unfortunately this addiction doesn’t just start out of nowhere and it will not just disappear over night. I know your mom says she is done with gambling and I am sure she really means it right now but realistically from what you write she isn’t there yet so yes I’m afraid she will probably relapse. This doesn’t mean that she doesn’t want to stop and there is no hope but she is just starting her journey.
To help her I would try being honest with her and not let her be dishonest with you. We have a habit of walking on eggshells around a CG as they can quite easily convince us that it is us who are nuts.
There is a thread on here called the F&F cycle. Have a look at that. Maybe if possible you could find a Gam Anon group … it can be invaluable providing you some much needed advice and support.
At the end of the day this is not your problem to fix. Please don’t feel guilty – you are young and have your studies and your life to live. You can support her but should not be putting more work into this than your mom.
Please take care and keep posting.