Should I let my girlfriend talk me into joining her and get cosmetic surgery too?

No. While going through an experience like cosmetic surgery with a friend can be rewarding in its own way, never allow anyone to "talk you into getting surgery." surgery carries risks and only when the benefits outweigh the risks as deemed by the patient (improved appearance, self-esteem, health, etc), should it be considered. Along the same lines, be wary of surgeons who try to make a "strong sell.".
No. Absolutely do not allow anyone into “talking you into” cosmetic surgical procedures. Internal motivation is one of the “keys to success” when it comes to patient satisfaction after surgical procedures.
Depends on your goal. People should only undergo cosmetic surgery procedures if they want it themselves. Having a cosmetic procedure for someone else is generally not a good idea. Surgery is a personal decision and should be entered into with confidence in your decision.
No. Sometimes women will let a friend go first to see what the whole experience is like and then proceed. Be supportive of your friend, but only do surgery if you want it!
Up to you. Decisions must be for each person for themselves. Do not do any procedures either for someone else or because they want you to do it. Each must answer as to what they are concerned about, why are they concerned, and are they willing to accept the risk for the reward of having surgery performed. Being supportive is different...Important. This is a personal decision and settled by you and doctor.