Maybe not the most interesting hand but looking for some insight on best flop line.

V1 - Terrible fish. Woman in her late 50s probably. Limps calls with almost any 2 preflop. Seen her limp with Q5s UTG + 1 and call a $15 raise pre heads up.

2 quick hand histories for this woman.
Hand 1
Someone raises to $5 pre, V calls, gets repopped to $35 PF. Opener calls, V calls.
$105 on flop. Board runout 5 5 J A K. on every street opener checks, V bets $10 and both the PF 3! and opener call. At showdown she wins with QJ. 3! had TT, not sure what opener had.

Hand 2
V opens to 15 in MP, V2 (3! from hand 1 calls). All others fold.
Flop($33) J 9 3r.
V bets $25 V2 raises to $100, V1 calls.
Turn($233) J 9 3 K
V1 checks, V2 ships $165 in. V1 calls.
River J 9 3 K 6
V1 shows QQ, V2 wins with J9.

On to the hand.
V1(~$400) - UTG +1
Hero($325) - MP - probably seen as TAGGY, been at table an hour, raised a few pots pre and took them down over limpers, a few raised and won with Cbet, have only shown down 1 small limped pot which was checked allstreets and I won with rivered middle pair.

Button Straddles for $5. Table is pretty loose PF even for raises.
SB folds, BB calls, V1 calls, fold to hero.
Hero raises with K K to $30. All fold except for V1.

Flop ($70) K 4 3
V1 bets $10
Hero?

This villain seems to like to make these small feeler bets. Part of me wants to just call and blast the turn, part of me, since she could have almost any 2 cards doesn't want to let her play a draw for $10 either if she has hearts of some straight draw but if she has a 1 pair type hand I don't want to push her out.

Call or raise and just hope she has a hand she is willing to go with? If we raise how much? If she checked I would have probably bet ~$45, should i treat her $10 donk basically like a check?

Yep, make it $55-$65. You could make a smaller raise if you were more nutted, but youve still got to protect. If she folds quickly you should raise 100% of your range next time you she does it. I bluff raise these bets a lot.

Given what we see in the history hands, V is never folding anything made to any reasonable bet size, so raise it up to something that allows you to get stacks in over three streets without overbetting.

Her donk is not just like a check, because with it and your call, the pot is $90 instead of $70, and your proposed bet would only be a $35 raise, making it only 39% of the pot instead of 64%. HUGE difference. I make it $75 here. Given her LP ways and her calls of big bets with overcards out, that doesn't seem likely to push her out to me.

If she calls that, pot is $220 OTT and we can bet $110, leaving an easy to call shove that is basically a "same bet" for the river.

I´m making it $70 to build the pot with the plan of 105-140 on the turn, and the rest of her stack on the river.

If you play her game of letting her make trivial small donk bets you won't be able to get real value for your made hands and you lose to too many draws.

The important thing to do is find out what her donking range is and if she folds her donks or not. This type is easy to beat once you get a handle on those two things because they are giving away too much information and/or setting themselves up to be bluffed. The key thing to know in this hand is if she donks draws or only made hands. There are a few easy marks that I would flat on this flop because their donking range doesn't include draws but does include a lot of single pairs that give up to a raise. Against that range hero is so strong that hero want to let her bet again before raising.

In general, raising this flop to as much as villain will pay to chase is the right solution. Most donks will have a lot of draws in their range on this sort of board because you make KX unlikely. Something $60-$70 seems good.