I'm not sure what your financial aid spokesperson meant by your loans will already be consolidated for you--they won't unless you apply for consolidation. But in a sense, you can think of your loans being "consolidated" if they're all with one lender. However, they're technically still different loans with different rates--just with one payment. But that's good, because then you can selectively pay off loans with higher interest if you want, rather than having one lump sum loan at an averaged (and rounded-up) interest rate.
Also, if/when you submit your PSLF eligibility (it's good to do it about once a year if you're not changing jobs) then your loans would all be transferred to FedLoan anyway, so even if your loans are split among multiple servicers, they wouldn't be for long.
PSLF and PAYE are two different things. PAYE is your payment plan (10% of AGI minus some percentage of the federal poverty level). PAYE does have its own forgiveness after 20 or 25 years. That forgiven amount is then taxed as income. (PSLF is tax-free)
PSLF is purely a forgiveness program--not a repayment plan. To be eligible for PSLF you have to make 10 years worth of eligible payments. IBR, PAYE, and the standard 10-year payment plan (plus ICR and maybe another one or two plans) are all eligible plans.
This means that you will enter PAYE as your repayment plan (assuming you're eligible). You technically never enter PSLF, since you don't apply for forgiveness until that 120'nd eligible payment is made. But you can track/document your payments as mentioned above. You basically give a form to your HR department and they fill out if you're at a non-profit and then they document how long you've been there and submit it to your loan servicer, who then looks at how many PSLF-eligible payments you made during that period. That then gets recorded (ie, you have made x PSLF-eligible payments, and you have 120-x payment remaining). I'd highly recommend you do that at the end of internship--while I still feel the odds of PSLF sticking around in its current form are low, at least this gets you in the door in the event that the gov't "grandfathers" people that already made documented payments into the program. Whether or not they'd do that, who knows, but it just takes a few minutes to get that form filled out and turned in, so you might as well.
You can keep doing PAYE as long as you want--if you decide to work at a for-profit agency then you just don't submit the PSLF eligibility forms, and just keep on making your PAYE payments. Of course, if you start making good money, then you should probably pay off those loans as quick as you can.