If your current snake is 2 1/2 years old and you're only feeding her one mouse every 10 days, that is not nearly enough food. Make sure to doublecheck your cage conditions and make sure she's got everything she needs; she may not feel secure enough, warm enough, humid enough, and is getting picky about her food as a result.

Even if she is only taking mice, a 2.5 year old snake needs more than what you are offering as food. If she's just a mouse eater, at least 2 or 3 should be offered weekly, more if she'll take them and/or if you plan on trying to breed her.

As far as the spider - my first advice is to focus on the snake you have to ensure she's properly cared for, then to see if you have enough money to get a proper set up for a new snake. From there, the price of whatever snake you decide you want is your call to make.

-Jen