she says I am being silly and insecure with myself.
Issue 1: dismissive of your thoughts/feelings.
She then preceded to list off how her ex partners used to bring her to climax.
Issue 2: Non-constructive, demeaning comparison to former lovers.
Specifically she mentioned one ex, who she regretably cheated on
Issue 3: Cheater. Regretably?
since she mentioned this I feel completely inadequate. I know that this is a ridiculous thing to say, perhaps immature of me
That depends entirely on what she is telling you and how she is telling it. There are ways to communicate that are constructive and ways to communicate that are demeaning. She seems good at demeaning and fails at constructive.
she has also talked about her travels with past partners, and I feel as if she has made too many memories with them for us to create our own life together.
Issue 4: Ongoing comparison to "better times" with other people. You can't live like this OP. You're not a fucking doormat. Tell her if you're not good enough she needs to get the fuck out. If you ARE good enough she needs to shut the fuck up with comparing you to other people.
I know that people have lives before their current relationship, but I am just not sure that I can deal with this.
No kidding. Why are you. Tell her you're not competing with her fucks from the past. If she likes your dick she can have it. If she like you she can have you. If not get the fuck out.
She would tell me on the phone about guys that were hitting on her, guys that she had met who she found cute and interesting.
She's an asshole who treats you like shit. Picture that for a moment. Are you some piece of shit getting pinched off by some asshole? If the answer is no then you need to "smooth move ex-lax" the way out of this relationship.
I am also very worried about telling my parents that I am dating a woman who is 16 years older than me, and 12 years younger than my mother.
You're getting ahead of yourself. You have yet to meet a woman 16 years older than you that is worth introducing to your parents.
Tell this woman that you had fun with her but she's become an annoyance so it's time for her to find her next piece of meat.