For your snake's sake I wouldn't give in easily, IMO I think learning how to open mouths is a very useful tool that you can learn: for the wellbeing of your current snake and any future snakes you aquire. Remember, just take a firm grip behind the head, and if she is a wiggler have someone hold her body firmly so you can have an extra hand free (ie to hold her head and the other hand to hold the q-tip in her mouth). If you're worried about the fuzz sticking to her teeth just cut the ends off.
And I agree with mpkeelee about the injections: if she does indeed have an RI you will most likely be doing the injections once a day for x amount of days and it will be very costly (and stressful) to take her in everyday to your vet so he/she can do it. Again, once you're shown how to do it it's a very useful skill to learn for any future occurances you might run into with a snake's health care.
If you're really worried I say do the vet appointment and go from there. If she has a RI then just take a deep breath and dive in there and do what you need to do to get her well (ie opening her mouth to check on her and doing the shots) - it could be a very good learning experience for you and benefit you in the future.
Good luck.