She probably needs to check with her former employer to see how long she can leave it open with them. Some companies require you to move the money in a certain number of months and some companies allow the 401(k) to remain open with them indefinitely even after separation.
If she has to move it, then she should be able to roll over the roth 401k money into a roth IRA and the traditional 401k money into a traditional IRA. I'm sure a phone call to vanguard (or whoever you choose) would be extremely beneficial and informative.
If she is allowed to leave the money with her old employer then it all comes down to the fund selection. If she is in good funds with super low expense ratios, then it may be best to leave the money in the 401k. Personally, I'd just call Vanguard and have them walk me through the steps to get the money into a roth/traditional IRA.
edit: missed the part where u said she has the option to leave the money...my bad.