Thank you very much for your replies! They have helped a lot. I do have a problem with saying "no" to people and guess it's my fault they take advantage of this. If I seem a bit too nervous about the whole thing, well recently I have had a huge fallout with (now an ex friend) because for the first time in my life I said that something was bothering me. The fact we weren't able to smooth things over makes me scared about losing more people over letting them know if I have a problem with them. I just know that I wouldn't react in this way and I applaude constructive criticism when it comes my way. I guess that this situation is perfect to exercise my character and show Maya she can't just take advantage of me. The problem is, she does see me as her closest friend here (me and Christina), and Christina and I are quite close (she has proven to be an amazing friend) but Christina has a very strong personality so Maya usually doesn't ask her what she asks me. I'll do my best and let you know how it goes!
Thank you again.